What CR would this monster be? [PF]

[TabletopGamer]

The monster is
Greater Doppelganger 3.0e
9 HD d8
Ability Scores: Str 12, Dex 17, Con 12,
Int 17, Wis 17, Cha 13
Skills: Bluff +13, Disguise +13,
Listen +15, Search +8, Sense
Motive +9, Spot +10

Alter Self
Can assume the shape of a Small or Medium Humaniod. Works like Alter Self cast by an 18th level Sorcerer. Remains in this form for as long as it likes or till it assumes a new one.

Use Magic Device
Can always use UMD regardless of form it is in.

Detect Thought
Cast like the spell of the same name by an 18th level Sorcerer, Save DC is 15. Can be suppressed or resumed with a free action.

Polymorph Rend
Can inflict 6d6 of damage to anyone under the effects of Polymorph, Shapechange, or Polymorph Other spells.

Immunities
Immune to Sleep, Charm, Hold Person and All-Other Mind Influencing Spells.

Consume Identity
A greater doppelganger who eats the brain of a Medium or Smaller Humaniod victim absorbs the mind, memories, and personality of that victum. After consuming a victims identity the doppelganger can assume the form 100% accurately and possesses the victims memories, abilities, and alignment. The excepts are Cleric Spells of 2nd or Higher Level, a paladins special abilities and other powers that are granted by deities.
When a doppelganger that has consumed three or more personalities consumes another it must make a will save (DC16) to avoid losing a previous personality.

In any case the doppelganger cannot have more consumed identities then it has Hit Dice, losing a random Identity from its earlier pool if it tries to exceed this limit. If a Doppelganger 'wearing' one of its consumed identities commits an act that runs counter to that form's alignment it is immediately forced into its base form for 1d10 rounds. In its base form a Doppelganger retains the basic memories of all identities it has consumed, though not deeper memories. Memories from previously consumed identities have been forced out by new identities fade quickly.
(Means if they lose the Id of the Priest they lose his specific memories as well and so can not only not shapeshift into him but also recall his knowledge.)

Skills
+4 Racial Bonus to Bluff and disguise Checks. When using Alter Self it recieves a +10 to Disguise Checks. If it can read an opponent's mind it gains another +4 Bonus on Bluff and Disguise checks. If using Alter Self to assume the Id of someone it has consumed it does not need to make a Disguise check.

Feats: Alertness, Ambidexterity, Blind-Fight,
Dodge, Expertise, Iron Will
It's Climate/Terran is Any Land and Underground
Solitary
Usually Neutral Evil
+ 4 NA
2 Slams (1d6)
its 3.0 Challenge Rating is 12 (Just noticed this; but CR is different in PF)

[rockdeworld]

It depends. Does it have a Slam attack, like the Doppelgangers in the monster manual, or does it use unarmed attacks? If not, and it hasn't consumed any identities, and it's only found in a dungeon, then I would rate it around CR 4, because the only way it deals damage is against Polymorphed enemies, or with identities it has consumed. Alter Self is so neutered in PF that it's almost ignorable, except as a plot device.

However, Consume Identity makes its CR range very wide. By RAW, if it consumes a 30th level Wizard, it gains 30th level wizard spellcasting. It can novem-stalt as anything except a paladin/cleric/oracle/inquisitor, at any level, and that makes it impossible to categorize. It could only really be given a CR under the following assumptions:

1. It has a statblock. This prevents every Greater Doppelganger from having 10th level druid, wizard and sorcerer spells, and saves GMs a lot of work.
2. It has a natural location. Fire elementals are expected to be encountered on the plane of fire, and their CR reflects that.
3. It has a set number and strength of identities.
4. It has set class skills. Every monster has this, and they have it for a reason.

Let's assume its base stats are 13/16/13/16/17/12 (10/11 array), its natural location is in a big city, and it has a base of 3 identities: a 6th level rogue, a 4th level fighter, and a 4th level ranger. And assume its skills support it. That gives it some sneaky abilities, including disguise and UMD to support them and complement its natural abilities, some fighting abilities, and some tracking abilities. It makes a decent bounty hunter. I'd rate that CR 6-7.

On the other hand, given that same ability score, but it had consumed a 9th level wizard, an 11th level magus, and a 10th level summoner. That CR is more on the level of OHGODRUN, and is pushing the limits of what a single monster should be. I'd rate that CR 10.

[TabletopGamer]

Again is only has access to one set of abilities when it is in that form. So it can only be Wizard while in the morph of a Wizard, Only a fighter in the form of a fighter.

I edited my original post with further information.

[rockdeworld]

Again is only has access to one set of abilities when it is in that form. So it can only be Wizard while in the morph of a Wizard, Only a fighter in the form of a fighter.

I edited my original post with further information.
Even if that were the case, it doesn't change the 30th level wizard problem. However, the rules you've supplied don't support your argument.

After consuming a victims identity the doppelganger can assume the form 100% accurately and possesses the victims memories, abilities, and alignment.
If it only gains those abilities while in that form, that sentence needs to read:
"After consuming a victim's identity, the doppelganger can assume the form with 100% accuracy and possess the victim's memories, abilities, and alignment while in that form."

Even then, it doesn't fix the problem of the doppelganger having the equivalent of at-will Shapechange-except-better-because-it-grants-spellcasting.

[TabletopGamer]

Its 3.0 some weird text errors are not a big surprise.

A greater doppelganger who eats the
brain of a Medium-size or smaller humanoid victim absorbs the
mind, memories, and personality of that victim. After consuming
a victim’s identity, the greater doppelganger can assume the
victim’s form with 100% accuracy and possess the victim’s memories,
abilities, and alignment. The only exceptions are cleric spells
of 2nd level or greater, a paladin’s special abilities, and other
powers that are granted by the deities. When a greater doppelganger
that has already consumed three or more personalities
consumes another, it must make a Will save (DC 16) to avoid
losing a random personality from those it consumed earlier. In
any case, the greater doppelganger cannot have more consumed
identities than it has Hit Dice, losing a random identity from its
earlier pool if it tries to exceed that limit. If a greater doppelganger
“wearing” one of its consumed identities commits an act
that runs counter to that form’s alignment, it is immediately
forced into its base form for 1d10 rounds. In its base form, a
greater doppelganger retains the basic memories of all the identities
it has consumed, though not deeper memories. Memories
from previously consumed identities that have been forced out by
new identities fade quickly.

That is the part from the monsters power. Perhaps I messed it up with Paraphrase.

also if you can beat and eat the brain of a lvl 30 Wizard.. maybe you deserve to be that powerful or you know.. already are in another way.

[rockdeworld]

That is the part from the monsters power. Perhaps I messed it up with Paraphrase.
No, what you quoted there and wrote above are the same. It's a problem prevalent in D&D, along with the "CR dartboard" approach.

also if you can beat and eat the brain of a lvl 30 Wizard.. maybe you deserve to be that powerful or you know.. already are in another way.
The point isn't whether you deserve level 30 casting or not, it's what makes a good guideline for DMs. Listing a creature as CR 12 when it can pull off better tricks than a great wyrm dragon is not a good design choice.

[TabletopGamer]

Agreed but again the DM would need to put you up against creatures as well as you need to eat their brain. This race is similar to the Illithid Savant but not quite as bad.

I just need a CR for it, it says CR 12 for 3.0 but yes its abilities are power, but if used by a GM what should I range it for. 12? 10? 14? 20?

[rockdeworld]

Agreed but again the DM would need to put you up against creatures as well as you need to eat their brain. This race is similar to the Illithid Savant but not quite as bad.

I just need a CR for it, it says CR 12 for 3.0 but yes its abilities are power, but if used by a GM what should I range it for. 12? 10? 14? 20?
I think you're confusing an NPC with a PC. PCs are the only ones the DM needs to "put up against creatures," NPCs are assumed to have done that already. So, again, its CR depends on the identities it has. If you want a blanket CR for it, then given that it can eat deities and gain their powers (since those powers aren't "granted" by a deity) make it CR 50. That number is ridiculous, because giving a set CR to a creature whose power varies so widely is ridiculous.

[Kudaku]

I have to agree with Rocktheworld - your question is akin to asking "what CR is a human?". Human includes Joe Dirt the unsuccessful dirt farmer on one side of the scale and Elminster on the other.

Without knowing more about the human in question, it's impossible to nail down a specific Challenge Rating.