Increase HD with templates.

[SolioFebalas]

Are there any templates that incresed class HD?

If i'am right, then:
Unseelie Fey Template (DM#304/Dragon Compendium) gives you d6.
Feral Template (SS) gives d10.

Any other ?

[Crake]

I believe necropolitan and lich increase class HD to d12?

Edit: I'm also pretty sure the feral HD increase only applies to racial HD

[gurgleflep]

As far as I know, all undead templates change your HD (both class and racial) to d12s.

[SolioFebalas]

Yea, but undead not counts. I hate lose Con, just hate.

[Biffoniacus_Furiou]

The two you mentioned only change your race hit dice, not class hit dice. The reason it's not explicitly stated in either of those templates is because they're from the 3.0 rules, which had in the general rules for templates that any changes like that only affect race hit dice.

The only thing you'll find that changes class hit dice is Undead.

[ArcturusV]

Though I ponder, couldn't you become undead, get your d12 on whatever, and have a feat like... Faerie Mysteries Initiate, so that way you still get a stat boost to your hit dice? I'm fairly certain that would work but not entirely so.

[Vaz]

Yes. It's a Tippy favourite.

[Fouredged Sword]

An elf dry lich can get both Int and Cha added to it's HP. Not shabby considering you can complete walker in the waste by level 11 or so with no LA.

Start as a desert elf (free heat endurance) and play a spontaneous domain casting ACF cleric. Take the sand and thirst domains. Take versatile spellcaster as your first level feat. You can now cast 3 spells from the sand or thirst domain as divine spells.

Build

Cloistered Cleric 1 / Walker in the waste 10 / Cleric PRC 9

Feats
1st - Versitle Spellcaster
3rd - Faerie Mysteries Initiate
6th - Free feats from here on out!

[Vaz]

With 16/16/16 in your mentals (upped to 18/16/16), that results in

Int to HP (+4/level), and Cha to HP (+3/level), you have +7/level; on a D6 base, that's 39+77 HP. Still, you've got to survive that far on 4+10d6(-2/level)HP; that works out as around 29HP.

Your mission, Mr Icy Hot...

[mattie_p]

Just to correct one misapprehension, not all undead change future hit dice to d12s. Vampires and lichs are examples of templates that do so. Necropolitan is an example of one that does not (this is commonly houseruled, I believe).

[Fouredged Sword]

Well, you have a rough time on levels 1-2, as you dump con hard, but you hang back and shoot with a bow for a while and hang out. At 3rd level you get int to HP, and can afford a +2 item. Pair that with, say, grey elf for a racial int bonus at the cost of more strength. You can get +5 or so HP per level without too much trouble.

Then at 11th level you get a retroactive Cha to HP, so that can again be boosted with items.

I would be surprised if you didn't end up with +14 or so bonus hp per HD on top of that nice 1d12. 400 hp or so at level 20 is nice on a caster who dumped con.