For starters, hello my name is Shadowclaimer, long time reader, first-time poster, been a DF player for a bit now, highly highly enjoying the game and the versatility it brings, done a bit of modding here and there and figured for what I can't mod, I might as well suggest.
Ontopic, lately seen a lot of discussion about magic around the web, people thinking its evil or such, that it has no place in DF etc. I've decided to throw out my take on it, the thing I've always pictured magic as is something that helps, but isn't required, its not something you should HAVE to have to survive anything, it should be a supplement for your fortress, giving you slightly more control over things. It should be a tool that in the hands of a capable player is powerful, but can be equally horrifying and full of consequences.
So here's my notes so far on the subject (Just me typing in notepad and discussing things with my fellow DF'ers)
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Magic: How to and Why
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Destruction (Destroys enemies and material)
-Fire (Flamethrower) (Offensive, chance to ignite foes)
-Water (Tidewalker) (Balanced, chance to drown foes)
-Earth (Earthshaper) (Defensive, chance to stun foes)
Alteration (Changes items in your fortress)
-Enchanting (Enchanter) (Add properties)
-Alchemy (Alchemist) (Change items)
-Psychology (Psychologist) (Changes people's thoughts/behaviors/skills)
Conjuration (Creates material, summons constructs, changes weather)
-Geomancy (Geomancer)
-Pyromancy (Pyromancer)
-Hydromancy (Hydromancer)
Libraries and Labs are various workshop-like structures that are available to dwarves wishing to study the art of magic (Alteration has Labs and Conjuration has Libraries). Conjuring Dwarves will choose "study" at the Library to gain skill in their chosen school of magic, you can actually order Conjurerers to perform a spell at their Library. Alteration followers will practice their skills on various people/objects/etc. and begin to get better at it (Experiment option at the Lab) eventually they will unlock spells you can specifically choose and choose specific targets (with chances for catastrophic failure for everyone, it won't be uncommon to see an apprentice Flamethrower murder all his fellow students in an accidental miscast or a Psychologist to accidentally make a Dwarf go berserk)
Destruction is a military form of magic, your Dwarves actually cast spells at a given Focii, which is a magical target, which trains them in their specific skill, the mastery they end up with is chosen based on what the Focii they are practicing with is designated as. As they get better their actual attack with the spell type is more powerful and effects are more likely. They must have a Spellbook chosen as their weapon. Flamethrowers are more offensive, Tidewalkers are a balance, and Earthshapers are more defensive.
Magic overall is a useful tool to assist your dwarfs, maybe you've been dying for some rain, you'll order your Hydromancer to call in a storm, however this could backfire, causing a drought for months maybe years. Maybe you need some powerful soldiers to supplement your army, or maybe you want to modify your Dwarves or their Items to your will. Magic will allow that, and will provide you a bit more control over your fortress.
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Religion: The Good, the Bad, and the Neutral
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Randomly a Dwarf may be chosen by his deity to be a Rambler, this dwarf will answer the call and will gain Apprentice in the Priest skill as he talks to Dwarves around the Fortress (as he normally would) he'll tell them how great his Deity is and how they should follow him. The more he converts the higher his skill gets. Eventually you may want to construct a Temple. Once you have a Temple you can select to go with the majority's Deity or the other ones worshipped in your fortress (This may anger some dwarves and make some happy, not like go crazy anger however). Depending on the Deity chosen your magic-using dwarves will gain access to a 4th skill type of each magic tree at their Libraries, Labs, and Focii. (Dependant on Good/Natural/Evil base for the Deity) Your Dwarfs that just hang out will go to the Temple and Worship (Priest skills are gained for former Ramblers), dwarfs that follow other Deities will go to other areas of the fort (Meeting halls or dark corners) and discuss their Deity still.
Good Magic (Light)
Destruction - Retribution (Avenger) (Offensive, frees converted/morphed allies)
Alteration - Emancipation (Emancipator) (cleanses magic effects on allies)
Conjuration - Restoration (Lightspeaker) (Summons Spirits to fight your foes)
Neutral Magic (Natural)
Destruction - Spellweaving (Spellweaver) (Balanced, chance to change enemies into creatures)
Alteration - Shifting (Druid) (Morphs enemies into natural creatures)
Conjuration - Restoration (Grovecaller) (Summons trees and plants, natural creatures)
Dark Magic (Dark)
Destruction - Shadow (Shadowcaster) (Offensive, chance to mind control)
Alteration - Assimilation (Assimilator) (Mind control enemies and naturals)
Conjuration - Necromancy (Necromancer) (Summons the dead to fight your foes)
Spheres in each Good/Neutral/Evil (need suggestions for changes)
GOOD - 48
Art
Beauty
Birth
Charity
Consolation
Courage
Crafts
Creation
Dance
Dawn
Day
Discipline
Duty
Family
Fame
Fertility
Festivals
Forgiveness
Freedom
Games
Generosity
Happiness
Healing
Hospitality
Inspiration
Justice
Laws
Light
Longevity
Love
Loyalty
Marriage
Mercy
Music
Oaths
Order
Painting
Poetry
Rebirth
Revelry
Rulership
Speech
Strength
Sun
Truth
Valor
Victory
Youth
NATURAL - 48
Agriculture
Animals
Balance
Boundaries
Caverns
Children
Coasts
Dreams
Earth
Fire
Fish
Fishing
Food
Fortresses
Hunting
Jewels
Lakes
Lightning
Luck
Metals
Minerals
Mist
Mountains
Nature
Oceans
Peace
Plants
Pregnancy
Rain
Rainbows
Rivers
Salt
Scholarship
Seasons
Sky
Song
Stars
Storms
Thunder
Trade
Travelers
Trees
Volcanos
Water
Weather
Wind
Wisdom
Writing
EVIL - 34
Blight
Chaos
Darkness
Death
Deformity
Depravity
Disease
Dusk
Fate
Gambling
Jealousy
Labor
Lies
Lust
Misery
Moon
Muck
Murder
Night
Nightmares
Persuasion
Revenge
Rumor
Sacrifice
Silence
Suicide
Theft
Thralldom
Torture
Treachery
Trickery
Twilight
War
Wealth
Also to note, when I refer to "Modify items" or such, I actually refer to a system of perks/downfalls that could exist on items, especially artifacts. The examples I had given to a friend I was talking to was that an item may have up to 5 properties given the quality of creation, these properties may be as simple as "Higher/Lower Value", maybe they are Pristine or Sloppy (more or less happiness from viewing it), maybe they burn forever (tables would be awkward like this), weapons could have various properties that would make them powerful in the hands of a warrior, cursed swords that speak to their wielder and slowly drain his soul could be possible, etc. more on that in other posts.