I did not write this. Just adding it here before it gets 'lost to the sands of time'...
Direct Copy-Paste from : http://www.killerbunnies.org/angband/god-220.html
[Last modified 2005-11-14. See below for recent changes.]
This spoiler attempts to describe and quantify the various in-game effects of worshipping ToME's gods -- the benefits and penalties, how to gain (or lose) piety, and so forth. Note that the spells (and access to other spell realms) provided by these gods is not listed here; see the ToME spell spoiler for that information.
Table of contents
Changelog and credits
The entries below for each god contain information under the following headings:
Normal piety change: Depending on what you're doing, your piety will increase or decrease with time; this heading details the rate of this change and what, if anything, you can do to alter it.
Affecting piety: Depending on your god, certain actions will increase or decrease your piety.
Piety effects: At certain piety levels you will gain various bonuses or penalties. For some of these, you must be praying for the bonus to take effect.
Relic quests: The properties of the "temple" dungeons in which you will occasionally go searching for lost relic pieces. Includes:
General layout properties, including floor types, "fill" types (the impassable areas between rooms) and outer/inner wall types used to generate rooms. Also noted is whether the dungeon is "ascending" (levels are shown as "LTm -5") or has "flat" levels" (up/down stairs are always at the edges and described as "paths to the next/previous area", like Mirkwood and the Barrow Downs) or "empty" levels (entire level is open space, with rooms interspersed, like Rhun).
Monster leveling relative to dungeon level, minimum number of monsters generated during level creation, and monster generation rate, expressed as the probability of a new monster being generated every 10 game turns (equal to one player turn at normal speed). Note that the first level of all temple dungeons will be level (L×2)/3, rounded down, where L is your level when you receive the quest.
Distribution of monster properties. This will be given as a list of "rules" with a probability distribution: some percent of monsters will have a certain set of properties, some percent will have another set, and so forth. If the listed percentages do not add up to 100%, then no restrictions are placed on the remaining fraction of monsters.
Distribution of types of objects found on floor or generated by chests or Scrolls of Acquirement, grouped as "treasure" (chests, crowns, rings, amulets, dragon armor), "combat" (weapons and armor, excluding those listed in other groups), "magic" (potions, scrolls, wands, staffs, rods, rod tips, parchments, runes, essences, junkarts, spellbooks, Mage Staffs and Demonology gear), and "tools" (light sources, cloaks, boots, spikes, diggers, food, flasks of oil, musical instruments, trapkits, iron spikes, and tools that can be wielded in the digger slot). If the listed percentages do not add up to 100%, the rest is allocated to "junk" (skeletons, empty bottles, eggs, and other junk items).
Other effects: Anything else that is affected by worshipping a particular god.
P denotes your current piety (displayed as "Pt" on the main screen).
(W@N) denotes "scaled" WIS, and is defined as (I×N)/37 rounded down to the nearest integer, where I is the stat index of your WIS -- which in turn is defined as your displayed WIS minus three (if you have turned off the "Stats are represented in a linear way" option, then for WIS values of 18/NNN the stat index is 15+NNN/10, to a maximum of 37 at 18/***).
Piety change rates are listed in game turns; 10 game turns is equivalent to one player turn at normal speed.
When discussing a monster or an attack on (or by) a monster, M will denote the level of the monster under discussion.
The godsEru IluvatarNormal piety change:
+(W@10) every 100 game turns, with a minimum of +1, if you are not praying, not in wilderness mode, and have done something other than resting during the last 100 game turns; no change otherwise. Affecting piety:
Destroying Blessed weapons decreases your piety by 10 times the base item's "native" level.
Killing a good monster decreases your piety by M×7. Piety effects:
If P>100000 and you are praying, then with probability 70 percent you will be resurrected upon death. After resurrection, your piety will be reset to -200000.
If you are praying, then an attack from an evil monster will be blocked with probability Q-(M×300) in 100000, where Q is the smaller of your piety and 50000.
Your maximum mana is increased by P/1000 percent, to a maximum of 35 percent. [Note that negative piety will reduce your maximum mana in the same manner, with no apparent minimum; a piety of -100000, for instance, would result in a -100% mana penalty.]
If P>10000, your WIS is increased by (P-1)/10000, to a maximum of +3. Relic quests:
Ascending, with flat levels, empty levels, circular rooms allowed and no doors, shafts or small levels; floor types dirt and grass, fill type mountains (unused), wall types granite wall/mountains.
Min starting monsters 14, generation rate 1/200, leveled to between half dungeon level and twice dungeon level.
Monster distribution: 50% evil, 50% flying.
Object distribution: 45% treasure, 5% combat, 45% magic, 5% tools. Other effects:
Wielding a non-Blessed edged weapon (sword, axe or polearm) will increase your spell failure probability by 25 percent and reduce your to-hit and damage bonus by 15. Manwe Sulimo Normal piety change:
-(4-(W@3)) every 300 game turns, with adjustments of -1 if you are praying and +(W@2) if you are of an elven race (Elf, Half-Elf, High-Elf, Dark-Elf or Wood-Elf), and a maximum of -1. Affecting piety:
Killing a good monster decreases your piety by M×10.
Killing an evil monster while praying increases your piety by M/2. Piety effects:
If you are praying, your speed is increased by P/5000, to a maximum of +7. [Note that negative piety will reduce your speed in the same manner, with no apparent minimum; a piety of -100000, for instance, would result in a -20 speed penalty.]
If P?2000, you gain levitation.
If P?7000 and you are praying, you gain free action.
If P?15000 and you are praying, you gain flight. Relic quests:
Ascending, caverns allowed, no doors or shafts; floor types "cloud-like vapor" and "condensing water", fill type hail-stone wall, wall types dense mist/hail-stone wall.
Min starting monsters 18, generation rate 1/160, leveled to twice dungeon level.
Monster distribution: 20% invisible, 20% orc or poison-resistant, 20% breathes poison or gravity, 20% casts poison-ball spell, 20% can fly.
Object distribution: 15% treasure, 25% combat, 55% magic, 5% tools. Tulkas Normal piety change:
-(4-(W@3)) every 300 game turns, with a maximum of -1, if you are praying; no change otherwise.
Killing an evil monster increases your piety by M/4, plus an additional M/4 if you are praying, plus an additional M/2 if you are praying and the monster is a demon. Piety effects:
If you are using the Weapon combat melee style, wielding a weapon, and praying, your damage bonuses will be increased as follows:
If P>1000, then with probability (W@130)-M percent the damage bonus from your weapon is doubled and the damage bonus from subskills of the Weaponmastery skill is tripled. This will be indicated by the message, "You feel the hand of Tulkas helping your blow."
Otherwise, the damage bonus from Weaponmastery subskills is doubled.
If P>5000, your CON is increased by (P-1)/5000, to a maximum of +3.
If P>10000, your STR is increased by ((P-5001)/5000), to a maximum of +3. Relic quests:
Normal dungeon, no destroyed areas allowed; floor type normal floor, fill type granite wall, wall types granite wall/granite wall.
Min starting monsters 20, generation rate 1/120, leveled to twice dungeon level.
Monster distribution: 100% demon or evil.
Object distribution: 10% treasure, 70% combat, 5% magic, 15% tools. Yavanna Kementari Normal piety change:
-(5-(W@3)) every 400 game turns, with an adjustment of +2 if you are an Ent and a maximum of -1, if you are not in wilderness mode and have done something other than resting during the last 400 game turns; no change otherwise. Affecting piety:
Attacking a pet or friendly monster that is an animal and not evil decreases your piety by M×4.
Completing the Lothlorien Spider quest increases your piety by 6000.
If a spell attack from you or any monster destroys a tree or small tree square, your piety is decreased by 50.
Charming a non-evil animal increases your piety by M×2.
Killing a demon, undead, or non-living monster increases your piety by M/2 if you are not praying.
Killing a monster while praying decreases your piety by M/2, plus an additional 3×M/2 if the monster is an animal. Piety effects:
If P?9000 and you are praying, you can pass through trees as though by the Tree walking ability. Relic quests:
Normal dungeon, water streamers allowed, no doors, shafts or destroyed areas, blocks genocide and recall-into; floor types dirt, grass and grass with flowers, fill type tree, wall types small tree/tree.
Min starting monsters 22, generation rate 1/120, leveled to between half dungeon level and dungeon level.
Monster distribution: 100% demon, undead or non-living.
Object distribution: 20% treasure, 10% combat, 30% magic, 40% tools. Other effects:
If you are praying and you are standing on grass (grass with flowers apparently doesn't count), your regeneration rate is increased by 200+(W@800). (For comparison, the normal regeneration rate is 197.) Melkor Bauglir Normal piety change:
-(8-(W@6)) every 300 game turns, with adjustments of -1 if you are praying and -(5-(W@4)) if you are of an elven race (Elf, Half-Elf, High-Elf, Dark-Elf or Wood-Elf), and a maximum of -1.
Killing a monster increases your piety by M×3 if it is good, 1+M/2 otherwise. Piety effects:
If P>5000 and you are praying, then each time you successfully hit a monster in melee, the effects of the Melkor spell Curse may be applied to the monster with no piety cost; the probability for each melee hit is (W@30)×(E@100)/M percent, where (E@100) is your scaled spell effect level for the Curse spell (see the spell spoiler for the definition of this notation).
If P?5500 and you are praying, and you take damage that leaves you with less than 25 percent of your maximum hit points, one or more friendly demons or undead (equal probability of either) will be summoned with probability (P/500)-10 percent. If P>10000, the summoned monsters will be greater demons or undead. The maximum number of monsters per summon is P/5000.
If P>10000, your STR, CON and CHR are increased by (P-1)/10000, to a maximum of +3; your INT and WIS are decreased by the same amount.
If P>5000 and you are praying, you gain invisibility.
If P>15000 and you are praying, you gain immunity to fire. Relic quests:
Normal dungeon, all levels are small, lava streamers allowed; floor types dirt, mud and nether mist (does 1d1 nether damage every 40 turns), fill type glass wall, wall types glass wall/granite wall.
Min starting monsters 24, generation rate 1/80, leveled to between half dungeon level and dungeon level.
Monster distribution: 20% good.
Object distribution: 25% treasure, 25% combat, 25% magic, 25% tools. Other effects:
Worshipping Melkor gains you access to the Udun magic school.
As a Melkor worshipper, you can sacrifice corpses and spellbooks on Melkor's altars (described as "Altars of Darkness" in-game) to gain piety. Sacrificing a corpse increases your piety by M×2; sacrificing a spellbook increases your piety by L×2, where L is the sum of the spell levels of all the spells in the book. Note that spellbooks that contain any Udun spells cannot be sacrificed.
You can also sacrifice hit points directly; each such sacrifice decreases your maximum hit points by 10 and, at your option, either increases your piety by 300×(W@6) or increases your melee damage by (W@4), with a minimum of 1. (Note that this bonus is recomputed retroactively as your WIS changes; that is, your current damage bonus from hit-point sacrifice equals your current (W@4) times the total number of times you've sacrificed hit points for damage bonus). Changelog and credits
Corrected damage bonus adjustments for Tulkas prayer, as noted by vfb
Typo, noted by user Maylith of the ToME forums.
"Updated" for 2.3.x. AFAICT, the described information did not change from 2.2.x.
Clarified that the damage bonus from Melkor hit-point sacrifice is based on current WIS.
Corrected Yavanna piety boost for charming animals.
Eru resurrection actually sets your piety to -200k rather than reducing it by 200k, as noted by user Elliot of the ToME forums.
Added notes on the effects of negative piety to Eru and Manwe entries.
Added table of contents.
Fixed assorted typos.
Added information about relic quest dungeons.
Mention the "hand of Tulkas" message explicitly as an indicator that the effect has occurred.
The "hand of Tulkas" melee bonus apparently only applies to weapon combat.