The Tavern

Tarrare The Gluttonous
http://en.wikipedia.org/wiki/Tarrare

The insatiable god of gluttony. Tarrare was a powerful demon who ascended to divinity by forcibly consuming a god. Tarrare’s hunger is infinite, it is predicted that in the end of days all of creation will be consumed by this terrible god’s gaping maw. Follower’s are filled with their lord’s unrelenting hunger, and are constantly driven forward in search of food. All must be consumed by the great maw of Tarrare.
Follower’s of Tarrare will be gifted with the Gourmand, and their stomach strengthened to better handle dangerous meats. Eventually follower’s will be given access to powerful gastrointestinal abilities, able to belch toxic fumes, and even eat their enemies alive.
Tarrare likes it when his follower’s consume food, (25% chance of +1 piety for eating)
Tarrare dislikes it when his follower’s go hungry (1 piety loss on average every 100 turns)
Tarrare strongly dislikes (penance) the violation of corpses- all must be consumed by the great maw.
Mummies, Vampires, and Spriggans cannot worship Tarrare due to their dietary restrictions.

Piety level (0): "Hungry Foo"
+Gourmand, Increase Corpse Drop Rate to 75%
Can eat food past engorged. Satiation past 12,000 is lost.
Permanently gain an additional rank of the Fast Metabolism Mutation. This is not lost if you later abandon Tarrare.

Piety level (*): "Voracious Foo"
Strengthened Digestion: Follower’s may eat any chunks found in the dungeon, including putrid and inedible. putrid and inedible chunks provide half nutrition.

Piety level (**): "Gluttonous Foo"
No new abilities.

Piety level (***): "Insatiable Foo"
Strengthened Genetics: Eating mutagenic chunks provides a 75% chance of a good mutation, 25% chance of a random mutation.

Piety level (****): "Ravenous Foo"
Belch: Cost- Hunger: Variable, 6 MP, Breath, 4-5 piety. Fills a cone shaped area in front of you with clouds. See Cloud Cone for Targeting. type of clouds is increased with hunger lost, invocations, and piety.
Sets Satiation Level to 3,500 All hunger lost is converted to spell power.
Spell Power = (Hunger lost / 100 + 1d Invocations * (Piety-100)/10)
Thin Mist (0-25)
Fog (25-50)
Noxious Clouds (50-100)
Poison Gas (100-150)
Miasma (150-199)
Acidic Clouds (200+)

Piety level (*****): "the Gaping Maw"
No new abilities.

Piety level (******): "Devourer of Worlds"
Praying at an Altar will gift you with Fangs 3. If this auxiliary attack causes damage against an opponent who can drop a corpse, gain 250 nutrition.

Divine Retribution
Passive
Decrease Corpse Drop Rate to 25% for duration of penance
Receive 50% less nutrition from all food sources

Active
Immediately reduce satiation level to Starving (500)
Summons multiple hostile Hungry Ghosts
Casts Corpse Rot
Causes you to pass out (as if you had berserked). Since it is not true paralysis, this effect goes through an amulet of stasis and thus cannot be avoided.
Polymorph player into Pig Form
Apply the weak status effect

Overview:
I wanted to base a god around the hunger mechanic. Clearly I will need to tweak some of the numbers around here and there. I want to get some feedback before taking further steps, however. The name is based off of that french dude in the wikipedia article I mentioned. Gourmand is a powerful intrinsic to have, and later the belch gives a powerful ranged attack option. Acidic Clouds are powerful throughout the game, but piety will be much harder to keep up in branches without corpses- especially with the accelerated decay. He also permanently increases a character's hunger rate, but the increased stomach capacity should more than make up for this.

I'd like to add a few more invocation abilities to the god, but I don't want to make him overly cluttered. Ideas I have toyed with is a slaying bonus based on satiation (-4 starving, -2 very hungry, -1 hungry, 0 satiated, 1 full, 2 very full, 3 engorged). Or a temporary buff that greatly increase hunger while activated. Any ideas are welcome! Enjoy

Belch seems problematic, mechanically. There are a bunch of cloud types, and I'd want different ones in different circumstances (in particular, I would often want fog) so I'd need to manage my satiation level which seems really fiddly. I think I'd belch, eat "enough" (where "enough" depends on invo) food to get my desired cloud, and belch again? Which would kind of work, but not entirely.

Having different abilities for the different clouds, with size depending on satiation, might be better.

Also, having the main piety gain mechanic be "chop corpses and eat them" would mean you spend a bunch of time cutting everything up (more time than normal, because there are more corpses now) and just eating them. It's effectively very similar to having corpses automatically eaten on kill (or when you step on them), but a lot more keypresses.

This god only has three somewhat meaningful abilities:
1: improved mutation roulette from a small subset of corpses; this steps of Jiyva and, to a lesser extent, Xom, but doesn't have a clear relationship to a god of hunger. Since the god has such a small number of powers, it seems like scumming for mutagenic chunks is meant to be a large part of this god's gameplay.
2: Belch. It does have the fiddliness issue njvack pointed out. If you removed fog and made more power more or less always better, that'd reduce the fiddliness. This seems like the god's signature power as written. I'm not sure this power is enough, especially considering that it only becomes available at 4*. This power largely mimics rod of clouds, which means that the god's signature power is available to most other characters if they happen to find a certain item.
3: Fangs 3. This is modestly strong, but not particularly impressive. Does the god give any compensation to creatures that already have fangs?

You tried to base this god on the food/hunger mechanic, but unfortunately food and hunger don't work very well in Crawl right now.

You might want to look at viewtopic.php?f=17&t=15026 (god of meat) for some ideas.