Help making a PrC (3.5) Demon Slayer Mage

[Clovis]

Hiyall,
This is my first attempt at making a prestige class. The following is based on my current PC, a vanilla human wizard at level 9 (was at 10 but then died and got rezzed). His racial enemy are demons, which are strongly featured in our campaign. Our DM has occasionally wondered why none of us players have used PrCs, so I thought I'd make one up. This PrC is intended to cover levels 11 to 15, and I intend to cap off with 5 levels of Archmage.

I'd very much appreciate any input, any comments! I don't know if this is overpowered or broken... I thought I'd up the will saves a bit and give some DR to increase survivability. So, here goes:


Demon Slayer PrC

You have seen a world a bit; you’re no longer a green adventurer, ready to believe everything. Upholding the law and order for the common good is your lifeblood. For this purpose you have sought, learnt and taught arcane magic. You are aligned with the cosmic forces of good to better help you in your mission. You have seen too much, too many friends to die in the hands of fiends. Now you feel enough is enough and you dedicate your considerable magical talent to hunt down and exterminate demons. In order to be able to better hurt demons you have fought them and studied them carefully. They no longer frighten you nor make you sick. You have toughened your body and mind to withstand magical and even physical battle with your sworn enemies, demons.

Hit Die
d4

Requirements
To qualify to become a demon slayer, a character must fulfil all the following criteria.
Skills
Knowledge (arcana) 10 ranks, Knowledge (demons) 5 ranks, Knowledge (planes) 5 ranks, Spellcraft 10 ranks.
Feats
At least two exalted feats.
Spells
Ability to cast 5th-level arcane spells.

Class Skills
The Demon Slayer’s class skills are Concentration, Knowledge and Spellcraft.

Skill points at each level
2 + Int modifier

DEMON SLAYER
{table=head]Level|Base Attack Bonus|Fort Save|Ref Save|Will Save|Special|Spells

1st|
+1|
+1|
+0|
+1|DR1, Hold demon|+1 level of existing spellcasting class

2nd|
+1/1|
+1|
+0|
+1|DR 2, Resist energies|+1 level of existing spellcasting class

3rd|
+1/2|
+1|
+1|
+2|DR 4, Banish demon|+1 level of existing spellcasting class

4th|
+2/2|
+2|
+1|
+2|DR 4, Poison immunity|+1 level of existing spellcasting class

5th|
+2/3|
+2|
+2|
+3|DR 5, Holy word|+1 level of existing spellcasting class[/table]


Class features

Weapon and armour proficiency
Demon Slayer gain no proficiency with weapons or armour. Normal wizard/sorcerer proficiencies apply.

Spells per day/Spells known
Upon gaining a new demon slayer level the character gains new spells per day (and spells known) as if he had gained a level in an arcane spellcasting class.

Class abilities
Hold demon
Once a day a 1st level demon slayer can hold a demon as if using the hold person spell. The demon’s spell resistance is automatically bypassed; there is a saving throw (DC 12 + slayer’s int/cha modifier)
Resist energies
A 2nd level demon slayer gains resistance to energies (acid, cold, fire and electricity) of 10.
Banish demon
At 3rd level a demon slayer can try to banish a demon once a day as if using the Banishment spell. The demon’s spell resistance is not applied; normal saving throw is applied.
Poison immunity
Prolonged contact with demons has rendered a demon slayer immune to all poisons.
Holy Word
A demon slayer’s affinity to good enables him to utter a Holy Word (as in the spell) once a day.
Damage reduction
Constant battle with the abyssal fiends has hardened the demon slayer’s body to shrug off minor damage.

[Glimbur]

Mechanically, you should specify which knowledges are class skills (probably all) and the caster levels for various spell-like abilities.

You have nonstandard BAB, Fort, Ref, and Will. Is there any particular reason for this?

Critically... it costs two feats to get in and a bunch of skills a wizard would have anyway. Knowledge(demons) is covered by knowledge(planes) unless there's a houserule. This class is entirely better than more levels of wizard. I find that to be poor design. Worse, it gives either more spells (wizards already cast spells) or strange things: resistances and DR are supposed to be more difficult to get.

So, you want a casting prestige class which is better at fighting demons. Have you considered Sacred Exorcist from Complete Divine? Paragnostic Apostle from Complete Champion is another caster PrC which is 5 levels and can help versus SR or increase your DC's against one type of monster, like a ranger's favored enemy. Chose CE outsiders and you're good to go.

[Zaydos]

I can't even figure out what their BAB is supposed to be. Non-standard saves I can get behind in this case.

Compared to a wizard you are trading 1 bonus feat you would have gotten for 5 levels of wizard, and 2 exalted feats for
much better Fort save (possibly best save)
possible +1 to Will (other contender for best save)
possible 1 point loss to Ref (eh, who cares)

Then you get Energy Resistance to 4 types (oh mathematically there goes the penalty to Ref, and then some) and DR 5.
Poison Immunity.
3 spell like abilities (CL should be listed for them).

Really it has no reason for the DR (barbarians don't even get but DR 5 over 20 levels). The energy resistance again is overkill. You'd do better just to give them d20 HD, it would possibly be weaker (+40 hp vs -5 or 10 damage from most everything) but one glance would still say that's broken. The spell-like abilities need Caster Levels.

[Clovis]

Thank you very much for your comments! I guess I went a bit overboard on my 1st try at a PrC... Time to tone it down.
I got the resistances from the Demonologist PrC at BoVD; it would make sense that any class whose purpose is to fight againts / consort with demons would have some kind of extra protection but then it seems to get a bit cheesy.
Thank you for the recommendations; I'll have a look at them. I didn't have access to those books and couldn't find a suitable PrC for my purposes. One of them might do the trick.
Anyway, my PC wizard already has access to divine spellcasting, if only for healing, and has two exalted feats (so he'll be lit like a beacon to demons with the detect good ability). Therefore, I wished to have access to some more divine magic to better combat demons.
Back to the proverbial drawing board...