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- Join Date
- Apr 2014
- The Netherlands
Zannu [3.5 Race] [Symbiotic aberration]
The Zannu are an insect-like species that originated on the astral planes in the distant past. Living and experiencing (different aspects of) life is the most important thing for a Zannu. As such the Zannu have spread out and have (quietly) integrated themselves among races and community all over the multi-verse.
Personality: At the very core of each Zannu is a love of life and a insatiable curiosity. While this could lead to a race of joyous explorers, the Zannu are actually a race of many a varied personality. While some will fling themselves into the face of danger to see what is going on ("I never saw a dragon that big before!"), others would cower in a dark corner, afraid of losing their life ("For how can one enjoy life, or see something new, if one is dead?").
But beyond their own innate personalities, most Zannu adopt an (mostly) outward personality that fits with the people it has chosen to live among.
Physical Description: Zannu look like the bastard child of a trilobite and a ray. Like the ray they are a single body without legs or other appendages and like the trilobite their body is inflexible. They use four skinny ectoplasmic tentacles to move themselves and interact with the world. These same tentacles are used by a Zannu to connect themselves to, and take control of, a physical body.
They are only between 4 and 8 inches long. The appearance of their outer shell depends on where they are born, varying between looking like metal, stone, wood or normal insect carapace. These differences are visual only, an adaptation to help them blend in with their surroundings or in some cases to deter predators.
Zannu do not die of old age. Some of the eldest Zannu are so old they have seen both the birth and death of deities that most other races would consider to be eternal. That said, Zannu's have a long life, but aren't immortal. Most will meet their end at the end of a sword or due to disease, or in rare cases, just losing the will to live.
As for births, the Zannu simply don't know (or much care) how they came to be (neither as a species, nor as an individual), they simply are. Those few that got curious and theorized on the matter came up with a number of theories (such as: growing out of other creatures, born from magic or even being born through the death of a previous Zannu) but nothing definitive has been found.
Relations: Zannu are social chameleons. Most blend in (almost) perfectly in which ever society they have decided to call home. While they know they will outlive most of the people they interact with, they feel no need to insulate themselves from the inevitable loss of their loved ones. Death (and pain) are merely another part of the experiences of life.
It should be noted that most Zannu never reveal their nature to those around them, and when they do, they reveal themselves only to the ones they love and trust the most. Of course, exceptions exist, especially amongst those Zannu that live among the more alien (and/or less morally up-tight) races.
Alignment: Zannu of all alignments exist, but as a whole they tend to gravitate towards lawful. In regards to the good VS. evil axis, the Zannu are all over the scale. Due to their "expendable" host bodies, they are often willing to make great sacrifices for others. But on the other hands, their ability to hide and manipulate (sometimes for millennia) also gives them the ability to be evil to a scale beyond the imagination of most races.
Zannu Lands: While they originally came from the astral plane, the Zannu have since spread across the multi-verse and no longer have a single place to call their home. Most individual Zannu will call which ever land they currently inhabit their home lands. However, in the depths of the astral plane there is a small temple, which has a name that, in the Zannu mind language, would translate to something close to the word "home".
Religion: The Zannu as a race don't have a particular attitude towards religion. Individual Zannu might take up the religion of their chosen society, but it is not an extremely common concept amongst them. Most will pay respect to whichever deity respect is owed, but nothing more.
Language: The Zannu communicate telepathically amongst themselves. When they focus they can also communicate telepathically with a single individual with whom they share a language. They quickly learn the common language of their birth lands.
Names: Amongst themselves, the Zannu have no names. Instead they use a combination of concepts, images and sensory impulse to indicate specific members of their species. In the world at large they often pick a name suitable to the race of their first host. Some Zannu stick with that name for the rest of their lives, others (subtly) change it with each new host.
Adventurers: When your goal in life is to see, do and experience new things, the life of an adventurer is just the thing for you. The Zannu are capable of being trained in just about everything, but most commonly have a preference for more mentally oriented tasks (after all, physically conditioning each new body gets tiresome after some time).
-4 Strength, -4 Dexterity, -4 Constitution, +2 Wisdom, -2 Charisma. Physically the Zannu are not impressive, at least without a host. They are however strong of will, even if their personalities are sometimes a bit unusual.
Type: Zannu are aberrations
Diminutive size: +4 bonus to Armor Class, +4 bonus on attack rolls, +12 bonus on Hide checks, 12 penalty on grapple checks, lifting and carrying limits 1/4 those of Medium characters.
Immobile: Zannu are naturally immobile, they have a movement speed of 0.
Astral movement: Zannu are at home on planes with subjective directional gravity. On such planes they need not make a wisdom check to set the direction of gravity.
Telepathy: A Zannu can communicate telepathically with others of its kind within 60ft. It can communicate with other creatures (one at a time) with which it shares a language from up to 10ft away.
Regional adaptation: A Zannu adapts to its birth region. In areas with the same climate as its birth region it has a +2 bonus on hiding in natural environments. It also learns the most common local language as its automatic language.
Automatic language: See regional adaptation. Bonus languages: Any (other than secret languages, such as Druidic).
Favorite class: Any. When determining whether a multiclass Zannu takes an experience point penalty, his or her highest-level class does not count.
Level Adjustment: +2
Blindsense: An un-joined Zannu has blindsense 60ft and blindsight 10ft. They are otherwise blind.
Astral movement: Un-joined Zannu have a fly speed of 60 (perfect) on planes with subjective directional gravity.
Ectoplasmic tentacles: An un-joined Zannu has 4 ectoplasmic tentacles. These tentacles can be used in one of three ways:
o Moving: For each tentacle used to move, the Zannu can move 5ft (max speed = 20ft when using all 4 tentacles). If the Zannu moves only 5ft, it is considered to be this turns 5ft step. Joining: An un-joined Zannu can bond with a suitable host that has been reduced to 0 Intelligence, 0 Wisdom and 0 Charisma. To do so he must grapple the host with all of his ectoplasmic tentacles (for details, see the joined creature template below OR the process in the 3rd post of this thread). This is a full round action that does 1d6 constitution damage to the host.
o Manipulating: For each tentacle used to manipulate, the Zannu can move a single object as if he used mage hand as a spell like ability (for each tentacle). Starting manipulation (no matter the amount of tentacles used) takes a standard turn. Maintaining it is a move action (again regardless of the amount of tentacles used).
o Probing: For each tentacle used to probe, the Zannu makes a touch attack against an opponent. If successful, the target must make a will save (DC = 10 + 1/2 HD + Int bonus) or have a single mental attribute (Zannu's choice) drained by 1d3.
Mage hand: A joined Zannu can use mage hand as a spell like ability at will, using its HD as caster level.
Darkvision: A joined Zannu can see in the dark up to 60 feet.
Un-joining: A joined Zannu can un-join either voluntarily, or because their host died.
o Voluntarily un-joining takes a full round action and does 1d6 non-lethal damage to the Zannu per HD the Zannu has. The host suffers no damage, but still has 0 Intelligence, Wisdom and Charisma.
o Un-joining due to a dead host is far more stressful to the Zannu. The un-joining is instantaneous and does 1d8 non lethal damage to the Zannu per HD the Zannu has and half again this amount in lethal damage.
Joined creature (Template)
[EDIT]Note that in the 3rd post of this thread a process description (instead of this template) is now shown for how to handle joining[/EDIT]
Spoiler: The joined creature templateA joined creature is created when a host joins with a Zannu "parasite". This joining can be either voluntary, for example if the host body is dying, or forced, after the Zannu has reduced the mental attributes of a target to 0 with its ectoplasmic tentacles.
The resultant joined creature is a mixture of the Zannu's knowledge, personality and mental abilities and the body and physical stats of the host.
Creating a joined creature
Joined is an acquired template that is added when a Zannu uses it's joining ability on a living creature of one of the following types: animal, humanoid, plant, or vermin. The host body must be of small size or larger.
A joined creature has characteristics of both the host race and the Zannu's race and class levels, as noted below.
Size and Type: The joined creatures type is aberration.
Hit Dice: A joined creature uses the hosts racial HD and Constitution modifier. All of the hosts class levels are lost. Further HD are gained through the Zannu's classes.
Speed: A joined creature uses the hosts speed and modes of movement, including maneuverability if applicable.
AC: Same as the host.
Attacks: A joined creature uses the hosts base attack bonus (from racial HD) and attack forms. Further progression is based on the Zannu's classes. All attacks use the hosts Strength or Dexterity modifier, as appropriate.
Special Attacks: A joined creature can use a special attack of either the host or the guest but cannot use both in the same round (unless it somehow has an additional partial action, such as from haste).
Special Qualities: A joined creature has the special qualities, both advantageous and disadvantageous, of both the host and the Zannu.
Base Saves: A joined creature always uses the saves of the Zannu (plus any bonuses from the host's racial HD).
Abilities: Use the physical scores (Strength, Dexterity, Constitution) of the host, and the mental scores (Intelligence, Wisdom, Charisma) of the Zannu.
Skills: A joined creature uses the Zannu's skill ranks, adjusted to account for the changed ability scores of the overall joined creature.
The original racial skill bonuses of the host still apply, but only for those skills related to physical traits. All physical skills in which the host has a racial skill bonus are considered to be class skills for the Zannu as long as it remains joined to that particular host.
Example: The high elves +2 bonus to on Listen, Search, and Spot checks still applies (as they just have better eyes and ears), but the Duergar +2 bonus on search checks to notice unusual stonework does not (it's more about the races love for stonework than anything about their eyes).
Feats: A joined creature retains the hosts racial and bonus feats (as long as they are related to physical ability and not to mental abilities) and gains further feats as the Zannu gains levels.
However, some abilities are so ingrained into a host body's muscle memory that they remain even after the host body has been taken over by the Zannu. Any weapon and armor proficiency the host possessed carry over to the joined creature as bonus feats.
Example: A level 1 human fighter is taken over as host. The joined creature does not gain its human bonus feat (it's from humanities adaptability, a mental trait), its fighter bonus feat (class related) or its 1st level feat (humans have no racial HD). However, the joined creature gains its proficiency with all armors, shields and all simple and martial weapons.
- Join Date
- Apr 2014
- The Netherlands
Re: Zannu [3.5 Race] [Symbiotic aberration]
This race was inspired by Admiral Squish's race of bone wearing oozes (the Sslak). After reading his race I immediately had visions of oozes seeping into people and playing body snatcher.
However, after thinking about it a bit, I figured it deserved to be a separate idea. (Plus, I love the concept of the symbiotic template, which the end result owes a lot to).
The main idea was to create a race that is suitable as a "guest" of a slightly adapted symbiotic template.
Currently, I've tried to reduce the potential unbalancing aspects of the template by removing the hosts class (and making the guest/Zannu the one gaining class levels), removing all mental feats/bonuses/abilities of the host and having to reduce a potential host to 0 in all 3 mental abilities before joining.
Things that need to be done (All help, comments and improvements welcome!):
Mind link racial ability (A mostly fluff ability where once per year all Zannu share their new experience with each other telepathically (from every corner of the multi-verse) - Something along the lines of a single legend lore question to be asked (re asked) at that time?)
How the joined creature reacts to being recently joined (How fast can he properly use his new body? Probably instantly stabilize, re-roll all dice against disease and poison... or something like that)
How to deal with racial hit dice (treat as LA? (but what if you go from a 6 racial hit die host to a 2 racial hit die host?) Only allow creature with less then X racial hit die? - For that matter, how to handle LA?)
How to deal with Ex/Su abilities (Of course the mental ones go bye bye, but what to do with the physical ones - some of the shape shift problems, but less so as you have to capture the creature alive first)
Aging of the host body (Should age normally... or maybe a bit slower then normal, maybe add some sort of saving throw (1 per year) to prevent the increase of age category?)
What feats does this race need? (Something that allows for more types of creatures to become hosts (monstrous humanoids at least) // maybe a feat to give the above bonuses to stop aging? // a feat to increase the amount of LA/racial HD you can have in your host body (or how many you can ignore).
Race specific prestige class (Similar some of the feat ideas above, something that allows you to ignore X LA, or racial HD, or take more types of hosts, or gain the Ex/Su abilities of the more powerful bodies? // Undead version, using either undead or corpses?)
- Join Date
- Apr 2014
- The Netherlands
Re: Zannu [3.5 Race] [Symbiotic aberration]
Instead of the template (as I tried to do earlier), it figured it might be a good idea to describe the process of making a joined creature step by step. (And maybe translate it back to a template like structure later.)
It has become a serious wall of text, so I'll try to make it readable through use of layout and (lots of) spoiler tags.
Selecting a host body
Before any descriptions can be made of the joining process, a suitable host needs to "procured".
Step 1: The (future) host must be reduced to 0 Intelligence, Wisdom and Charisma.
Step 2: If the host body is suitable, the Zannu can bond with it by grappling it with all 4 ectoplasmic tentacles.
Suitable hosts -A host body is suitable if:
It is one of the following types: animal, humanoid, plant, or vermin.
Its size is small or larger.
Its racial HD + Level adjustment does not exceed 2 (A single racial hit die is ignored, as usual).
It is still alive (but reduced to 0 in all three mental stats).
Preparing to change the host body
The joined creature owes many of its features to the host body. As such the changes to the host are described first.
Step 3: Split the statistics of the host body into the following parts: Level related, Race related and Circumstance related.
Level related includes, but is not limited to: Class levels (and all features of those class levels, including hit die and increased saves), feats gained due to level up and skills gained from level ups.
Race related includes, but is not limited to: Bonus feats, racial hit die, size, movement speeds and racial bonuses to skills.
Circumstance related are all things that don't fit into the above categories, such as: Age related bonuses/penalties, changes in appearance and physiology (such as having lost an arm) and all other features of the host body related to outside sources.
Modifying the host body - Circumstance related
We'll start with the easiest, the circumstance related features of the host body.
Step 4: Remove only those circumstantial bonuses/features that are related to (mostly) mental abilities of the host.
Also remove abilities granted by gods (or other powerful beings) who would both know the Zannu has joined with the host and disapprove.
Spoiler: Examples related to step 4Example: Jill the human has lost her left arm in a battle. For her bravery in that battle her god granted her the ability to see through any illusion.
If Jill's body was to be used as a host body, the joined creature would not have a left arm (it won't miraculously re-grow), but would not be able to see through any illusion (the god would have no reason to grant such a boon to the Zannu).
Example: Jack the elf is an old man, his strength, dexterity and constitution have started to fail him. His years of study have granted him incredible knowledge (a +2 inherent bonus to all knowledge skills). The entity that protects the order of monks that Jack is a member of has altered his eyes so that he can see in the dark almost as well as he can in broad daylight.
If Jack's body was to be used as a host body, the joined creature would still be old and have a reduce strength, dexterity and constitution (he would not miraculously become younger). The joined creature would not have Jacks bonus to knowledge skills (which was purely a mental ability of Jack, not a feature of his body or some magic that affected him), but he would still have Jack's ability to see in the dark (as his eyes were actually changed, not merely "blessed" by the entity).
Step 5: Record which circumstantial features remain.
Rule of thumb: Be generous - Keep any circumstance related feature that is not (mostly) related to the hosts former personality/mental ability or part of some (non permanently physically altering) blessing.
Modifying the host body - Level related
Handling the host bodies level related features is somewhat more complex, but still significantly easier than the race related features. As a rule, all but a few of them are removed.
Step 6: Ignore all of the host bodies skills (the actual values), saving throws and hit points.
Step 7: Identify any level related feature that could be attributed (near) exclusively to the hosts body (muscles, bones, skin and/or muscle memory). [In case (many) feats gained through level seem to apply, the DM should feel free to be strict and limit the amount of "bonus feats" the joined creature gains]
Weapon and armor proficiency feats are considered to be related to muscle memory, as would the improved unarmed strike feat.
On the other hand, feat such as weapon focus, while mostly physical also have a mental aspect and are removed.
Spell casting and other features that are very much dependant on mental abilities or the blessing of one's patron deity are always removed.
Transformational classes are a special case requiring a case by case analysis (especially for un-completed transformational classes). Completed transformational classes should be split into abilities that are (only) class related and abilities that are part of the "new race" of the host. The new race/template of the host body is handled under race related features.
Spoiler: Examples related to step 7Example(part 1): Tim the barbarian's (7) body is used as a host. His saving throws and barbarian hit die are ignored. Of his class features, only fast movement (muscle related) and damage reduction 1/- (body related) remain. He also remains proficient with all simple and martial weapons, light armor, medium armor, and shields (except tower shields).
Example (part 2): Should Tim have been a level 17 barbarian, the joined creature would have the "tireless rage" feature (but not the ability to rage, nor would his rages (gained through other sources) be "greater").
Example: Tom the sorcerer (6) dragon disciple (10) would (if he could be a host body, which a half dragon normally would not be) be treated as a Half dragon with 6 levels of sorcerer. If the Vannu is strong enough to take Tom as a host body, the half dragon part would be assessed under race related features. 6 levels of sorcerer would grant the host body proficiency with simple weapons (related to muscle memory). Tom's 3 level related feats were all related to spell casting and are also lost.
Step 8: Record which level related features (if any) remain.
Rule of thumb: Be vicious - Beyond weapon/armor proficiencies remove any level related feature that can be argued to have (more than a minute) mental component.
Modifying the host body - Race related
Finally it is time to analyze the race related features of the host body. The joined creature will possess most of the racial features of its host body, with the exception of the (mostly) mental features.
Step 9: The host body's racial hit die are preserved as bonus hit die of the joined creature. They (along with the host body's level adjustment) do not affect the joined creature's ECL (the Zannu is already paying for them with its own LA).
Step 10: The host's racial skill bonuses are preserved as long as the bonuses are related to racial features that are not (mostly) mental.
Special: A starting Zannu character that has been in possession of his "original" host body for a long time, might be argued to possess/have acquired some of the mental aspects of his host bodies race. This decision is up to individual DM's, but should be lost if the Zannu changes hosts and the features are (in any way) dependent on any physical feature of the host body.
Spoiler: Examples related to step 10Example: Lars the high elf has a +2 racial bonus on Listen, Search, and Spot checks. These bonuses are related to having better eyes and ears than most races. As such, if Lars' body was to be used as a host body, the joined creature would also gain these bonuses.
Example (part 1): Lee the deep dwarf has a + 2 racial bonus on Search checks to notice unusual stonework. This has more to do with the race's fascination with stonework than with having better eyes. As such, if Lee's body was to be used as a host body, the joined creature would not gain this bonus (Nor the bonuses to craft and appraise. Or the bonuses against orcs, goblins and giants (a combination of training and hatred).
Example (part 2): However, if the Zannu has been in possession of the deep dwarf's body since childhood, he might have grown up with a hatred towards goblins and orcs similar to a normal deep dwarf and gain the bonuses to attack those races.
Step 11: Skills the host possessed are not transferred to the joined creature, at least not directly. Instead the joined creature gains a racial bonus to certain skills based on the host body's skills and racial hit dice.
The joined creature gains a +1 (increase) racial bonus per racial hit die to any physical skills that the host had skill ranks in. The joined creature gains a +1 (increase) racial bonus per two racial hit dice to any partial physical skills that the host had skill ranks in. Mental skills don't transfer at all.
These increases to racial bonuses can't be higher than the host body's rank in a skill.
Spoiler: Classification of the skillsPhysical skills: Climb, Jump, Swim.
Partial physical skills: Balance, Control Shape, Escape Artist, Hide, Listen, Move Silently, Ride, Search, Spot, Tumble.
Mental skills: Appraise, Autohypnosis, Bluff, Concentration, Craft, Decipher Script, Diplomacy, Disable Device, Disguise, Forgery, Gather Information, Handle Animal, Heal, Intimidate, Knowledge, Open Lock, Perform, Psicraft, Profession, Sense Motive, Sleight of Hand, Speak Language, Spellcraft, Survival, Use Magic Device, Use Psionic Device, Use Rope.
Note: These classifications don't always line up with which racial skill bonuses that are maintained in step 10.
Example: A doppelganger host would gain the +4 racial bonus on Bluff and Disguise checks (step 10) because they are related to the adaptability of its body, but would not gain any further increase in those skills (step 11) because the additional skill ranks represent (partially) mental training.
Spoiler: Examples related to step 11Example: A Zannu has taken a donkey as a host. The donkey has 2 racial hit dice and the following skill ranks: Balance +3, Listen +3, Spot +2. All of these skills are partially physical skills, as such the joined creature gets a +1 racial bonus to spot, listen and balance (and the donkey's normal +2 racial bonus on Balance checks).
Example: The Zannu has managed to take a shambling mound as a host. It has 8 racial hit dice and the following skills: Hide +3, Listen +8, Move Silently +8. All of these skills are partially physical skills, as such the joined creature gets a +4 racial bonus to listen and move silently and a +3 racial bonus to hide (would be +4, but it can't exceed the shambling mound's +3 hide skill).
Step 12: The host's size, speed, physical attributes (Strength, Dexterity, Constitution), attack methods, armor class , space and reach transfer to the joined creature. Its appearance also remains the same.
Step 13: The joined creature is always of the aberration type, but it retains most traits of its former type. It is affected by spells and abilities as if it was of both types. Type traits that are related to absence of a (normal) mind are lost. Finally immunities related to a lack of a specific anatomy are replaced with a 75% chance failure (similar to moderate fortification) as the host's body is still immune, but the Zannu itself can be targeted (but not easily).
Spoiler: Example related to step 13Example: A treant turned host becomes an aberration, but it still doesn't need to sleep. It now has a 75% chance of avoiding critical strikes (instead of 100%) and can now be affected by mind-affecting effects. Bane weapons against both plants and aberrations do extra damage to the resultant joined creature and spells that only target plants still work on it.
Step 14: Special attacks and special qualities. Here it becomes somewhat murky, but we once again apply our mantra: "If it is (mostly) mental, it does not transfer". Supernatural abilities are almost always removed as a result of this.
Note: It is quite possible that the removal of (most) of a host's supernatural and mental abilities significantly reduces its strength/threat level. In such a case, consider reducing (or in extreme case removing) it's level adjustment.
Spoiler: Example related to step 14Example: A silver dragon host would retain its breath weapon and cloud walking (even though they are supernatural) as they are aspects of its (magical) body. They would however lose their spell like abilities and alternate form ability. Its extraordinary abilities (such as: spell resistance, damage reduction and frightful presence) are retained as well.
Step 15: Record which race related features remain. (Or in many cases (because it is easier) record which are changed/removed.)
Rule of thumb: Be judicious - A joined Zannu is very much like a member of his host body's race and is generally paying for his racial hit dice and level adjustment through his own +2 level adjustment. So let him keep what is appropriate and reduce level adjustments when (too) much is removed from the host.
At this point most of the features of the host side of the joined creature are known. Now we need to add the Zannu part of the joined creature and do some final mop up.
Step 16: Adding the Zannu:
The Zannu's mental attributes (Intelligence, Wisdom and Charisma) become the mental attributes of the joined creature.
The Zannu's class levels are added to the joined creature.
The Zannu's special qualities are added to the joined creature (both the normal ones and those specifically mentioned under "joined").
The Zannu's skills become the skills of the joined creature (remember the racial bonuses that the host brings to the joined creature).
The Zannu's saves are used, but they are augmented with the new physical attributes that the joined creature possesses.
The joined creature's maximum HP is determined by adding together "the Zannu's max hp" + "the hosts racial hit dice (rerolled)" and is modified for the new constitution modifier of the joined creature.
The joined creatures ECL remains equal to the Zannu's class levels plus its level adjustment (normally +2).
Step 17: Getting up and starting to go.
The joined creature's current HP = "Zannu's current HP" plus "the hosts racial hit dice (rerolled)" minus "the damage the host had suffered at the time of joining". If this puts the joined creatures HP below 0, it automatically stabilizes. If it's HP drops below -10 it needs to make a fortitude save (DC = 10 + amount of HP under -10). If successful it becomes stable with -9 HP, if not the host dies and the Zannu is forcefully un-joined.
If the host was suffering from disease and/or poison, the joined creature immediately gets 2 additional saving throws (per disease/poison) to overcome it. The joined creature gets to make these saving throws even if, under normal circumstances, no more saving throws are allowed.
For every bonus racial HD the newly joined creature has, it gets a -1 penalty to reflex saves, AC and attack rolls. Every day the Zannu is in its new host, those penalties drop by 1.
Step 18: Go play with your newly joined Zannu.
What happens when the Zannu gets a new host
Finally there a number of problems that occur when the Zannu takes a new host. Among other things it can find itself in-eligible for certain feats and prestige classes. Most of these problems can't be handled with direct rules (or at least not in any way that is satisfactory in all cases), but I'll try to give some basic ideas on how to handle them.
Of course the simplest method would be to avoid such things altogether (always taking similar hosts or taking feats/classes that only depend on the Zannu part of the joined creature), but as the ever experimenting Zannu would say to that "Been there, done that, boring!".
Spoiler: Situations that might occur and how to handle themBecoming in-eligible for feats: The most basic way of handling this would be to allow the Zannu to retrain all feats it has become in-eligible for (with the normal time required, and possibly the cost as well). This has the downside of allowing it to completely altering its training when it gets a new body, but the time it has to invest in it nicely represent the Zannu getting used to its new body.
The most harsh way of handling it is to just say "too bad". While this is an option, it does force a Zannu player into one of three situations:
The Zannu only takes feats linked to mental ability scores (and other things that don't change between hosts), railroading him out of certain play styles/feat choices.
The Zannu always takes/looks for a specific type of host. While this is a valid playing style (and quite similar to how normal races play the game), it does ruin some of the "body snatcher" feel of the Zannu.
Or the Zannu can choose whatever feats and hosts it prefers, and accepts that with certain hosts it will be limited to some degree.
Probably the most fair way of handling it (to both the Zannu who wants to occasionally switch hosts and the rest of the players who are "stuck" with their choices, is to combine all of the above to some degree.
Initially the Zannu is stuck with whatever feats it had before joining with its new host. But, after getting used to its new body (see above), it is allowed to retrain a single feat (taking the normal 2 weeks for retraining). At every level up after that, the Zannu is allowed to retrain two feats (instead of the normal one feat - but both must be ones it is now unable to qualify for), until it no longer possesses any of the feats that it was in-eligible for due to its new host. Should the Zannu ever take another host of the type it was before, it is forced to retrain back to the feats it had back then using the same process.
Becoming in-eligible for prestige classes: A Zannu who becomes in-eligible for a prestige class it possesses levels in, is unable to continue taking levels in that prestige class. Beyond that it can't use those features of a prestige class related to whatever the Zannu no longer possesses that is required for the prestige class.
Example (part 1): A Zannu with a Dwarven host has 4 levels in the Dwarven defender prestige class. After the host dies it takes an Elven host. Its alignment hasn't changed, it still possesses the necessary BaB and it is still eligible for the required feats: Dodge, Endurance, Toughness. It retains all features of the Dwarven defender class but is unable to gain more levels in it. [The only thing it lost was being a Dwarf]
Example (part 2): A while later the same Zannu takes an orc host. This host has a low dexterity score and the Zannu no longer meets the requirements for the dodge feat. The Zannu is still unable to take levels in the Dwarven defender class, but it also loses the uncanny dodge and trap sense class features (the class features related to the dodge feat).
Transformational classes: These classes work in the same way as other prestige classes, but the transformational part of the class is only slowly applied to the new host. When the Zannu takes a new host, only the non transformational aspects of the class are gained immediately. Each week after taking its new host the Zannu applies a single level worth of transformational effects (until it catches up with its actual level in the class).
Example: A Zannu has 7 levels in the dragon disciple class when it takes a new host. It immediately gains the blindsense 30ft and bonus spells. After 1 week its natural armor increases by 1. The next week its strength increases by 2 and it gains the "claws and bite" class feature. Until after 7 weeks it is a normal member of its class. After that it can gain levels as normal in the dragon disciple class (if it gains level in dragon disciple before hand, those new levels also apply at a 1 per week basis until they catch up).
Special: As the half-dragon template can be added to a dragon, a Zannu who takes a dragon or half-dragon host gains the benefits of the dragon disciple class (and can continue to take levels in the class, even though its race would normally make it unable to qualify).
Yes, its a lot of reading, but I feel this way, a joined Zannu might actually be somewhat balanced and enjoyable.
Next up, Zannu specific prestige classes (The body snatcher, which increases the amount of racial HD and (and to a far lesser degree) LA your hosts may have, as well as adding some other types your hosts can be AND the puppet master, which increase the amount of super natural (and maybe some mental) abilities your host body gets to keep, and make it easier for the Zannu to switch between hosts).
Also, maybe write up an example joining or two, to clarify and examplify the whole process.