Gods

Taurog, the god of battle:
Gives attack bonuses for physical kills; penalizes for use of magic.
Good for physical combat specialists.

The Earthmother:
Rewards the act of petrification.
Good for gorgons. Floods the level in stone upon renouncement. Renouncement can be used to the advantage of a transmuter.

Glowing Guradian:
Gives protection from poison, and rewards the slaying of undead; dislikes the use of unholy magic.
Good when fighting many undead.

Binlor Ironshield:
Gives stat bonuses for long-term loyalty and gold for mining.

Dracul:
Rewards killing with up to 30% lifesteal. Deducts maximum health when recruiting, punishes the killing of undead, detests holy spells and holy men.
Good for vampires and physical combat specialists. Proceed with caution when serving this God. Do not renounce.

Tikki Tooki:
Rewards displays of skills (killing an enemy in normal combat without taking damage) by curing ailments and increasing nimbleness.
Good for rogues and assassins. If entertained (number of skillful kills?), Tikki Tooki will allow renouncing with no consequence; otherwise he will destroy your health potions.

Jehora Jeheyu, god of destruction:
Rewards damage taken with increased health and damage dealt with increased attack power. Removes first strike and punishes the use of magic to protect own life.
Good for units that do not rely on defensive magic for their survival.

Mystera Annur:
Reduces physical damage to 1 but provides additional maximum mana with every level up and on each kill. Attack power is returned if denounced, but renouncing will cause glyphs to break after use.
Good for wizards and bloodmages.

The Pactmaker:
Somewhat mysterious. Decreases stats when you begin to follow him. Provides additional experience for each kill, 1 max mana with each level up, and probably some other stuff.
Good for assassins. Does nothing upon renouncement.