The effectiveness of each discipline is also supported by the the attributes they require:
Elemental magick's supporting attribute is intelligence.
Divination magick's supporting attribute is wisdom.
Magick & the Perception Attribute
If you're planning to play as a mage in Book II, the Perception attribute seems to be the key driver of rapid mana regeneration: If you focus on optimizing the Perception attribute as much as you can in your first few level-ups, your mana points will regenerate quickly even while you're just walking around performing other tasks. (We found that loading attribute points into Perception was so effective that we never needed to invest scarce skill points into the Meditation skill that is also designed to increase mana regeneration.) While not vital to winning a pacifist run, high Perception and mana regeneration really helps, since you can cast even high-level spells repeatedly without running out of mana and having to consume comparatively scarce (and expense) mana potions.
Elemental magick skill required: 1
Minimum intelligence required to cast spells: 15
Sparkling Wonder: This is probably our single favorite spell for a pacifist run. It causes enemies to become intimidated by an inherently harmless display of dazzling lights and temporarily "flee in terror" to get away from you. This usually works for at least a short time on most enemies found from the very start to the very end of the whole game. The effectiveness depends on the casting level, but even to a level 1 mage, it can cause enemies like Catacomb Rats to flee and get out of your way for up to 20 turns per casting level.
Unlike the Divination spell Entangle (which often wouldn't work at all on higher level creatures even at its highest casting level), we found that the Sparkling Wonder spell remained surprisingly effective even on powerful creatures, if cast at its maximum level. (The effect on stronger creatures often lasts for only a few turns, but even turning away a hostile foe for 1-2 turns can be very helpful right up to the end of the game.)
Sonic Blast: We didn't end up using this much, but it has good potential since it temporarily stuns nearby targets and lowers their offensive (as well as defensive) abilities.
Fire Dart: This is a low-level spell that a mage can use to attack, but it also has its uses for even a strict pacifist mage also, since it can be used to shoot at inanimate objects like powder kegs (to blow apart rock obstructions from a key path, for example). In some cases in the Eschalon trilogy, a firedart or similar spell can also be used (along with thrown objects) to throw a switch from a distance, which is sometimes required to solve puzzles when a key lever is inaccessible.
Reveal Map: This temporarily grants points in the cartography skill, enabling you to make maps. (Cartography is always an optional skill in the Eschalon trilogy, but this spell is a good find if you want to map everything out yourself, because then you can conserve both gold and/or scarce skill points without having to spend them training in the cartography skill.)
Gravedigger's Flame: This spell creates a magickal torch floating over your head to illuminate the surrounding area. The only problem with it is that darkness is often your friend on a pacifist run, since it causes penalties to any enemies that try to attack you, and can even help you remain completely unseen if you're using the Hide in Shadows skill.
Draw Water: This allows you draw water out of the humidity in the air around you and fill your water skins without having to find a clean water source, which could be useful in dungeons that you can't egress from easily. This will also give you the luxury of being less conservative about carrying around a lot of extra pounds of water skins with you, which can make a difference when carrying a lot of treasure out of dungeons.
Element Armor: This could be very useful to you since it creates additional resistance to elemental damage. (We never used it much, but there are places with powerful traps that this could probably protect you from.)
Predator Sight: This enables the caster to see foes illuminated in glowing green even in pitch-dark environments. (The main use of this is to reduce penalties for combat players who want to attack other creatures in the dark, so we didn't have a need for it in our pacifist campaigns, and just sold the scrolls for more gold instead.)
Elemental Magick: Tier 2
Elemental magick skill required: 5
Minimum intelligence required to cast spells: 20
Dense Nimbus: This spell creates a bubble of highly pressurized air around you that will cause the majority of projectiles fired by enemies to bounce off without striking you. No matter how nimble you are in evading melee attackers, there are a number of places where ranged attacking enemies will probably be a serious nuisance unless you have this spell on a pacifist run, and it can easily make the difference between easily bypassing ranged attackers vs being slain quickly by their projectiles.
Lock Melt: This spell concentrates intense heat that can actually melt locks off doors, making it (theoretically) unnecessary to use lockpicks or learn the Pick Locks skill—at least earlier on in the game. However, we'll also warn in advance that even though you can open most locks in Eschalon Book II with this spell at a high casting level, you won't be able to open them all, and there are at least two locks near the end of the game that are immune to the Lock Melt spell. (The only other way to open those doors would be to kill the foes carrying the keys, which could potentially spoil a pacifist challenger's ambition to win a zero kill run very close to the end, so we'd recommend that you eventually learn Pick Locks even if you're an elemental mage.)
Also, picking any lock also rewards you with more nonviolent experience points (with the exact xp awards depending on the strength of the lock), but melting a lock with the Lock Melt spell doesn't reward you with extra xp at all.
Trapkill: This is another great spell to have, because it can disarm traps without any need to allocate scarce skill points in "Skullduggery," the trap disarming skill. (This can save you from taking a lot of damage and being afflicted with poisons or disease from traps, so is well worth learning.) However, if you decided to invest skill points in Skullduggery instead, disarming a trap will award you with xp when you succeed, and casting Trapkill won't.
Chameleon: This spell is theoretically useful on a pacifist run since it enables you to blend in with your environment to become harder for enemies to hit. (It won't actually make you invisible or hidden in the shadows, but we occasionally used it in tough spots where we needed to "run a gauntlet" without being struck dead, and it probably helped.)
Fireball: This creates a fireball that will explode and do damage to surrounding beings (or inanimate objects). It could theoretically be useful in the same way as firedart, but with higher risks of accidentally damaging foes.
Enkindled Weapon: This adds fire damage to any melee weapon the mage is wielding, but since we always sold all the weapons we found for gold, we never tried it, and sold the scrolls for this for more gold.
Toxic Element: This would create a vaporous mist to poison enemies to inflict damage, so we always just sold it for some gold.
Compress Atmosphere: This is another attack spell that deals crushing damage to foes, so we just sold any scrolls for this one too.
Elemental Magick, Tier 3
Elemental magick skill required: 11
Minimum intelligence required to cast spells: 25
Invisibility: This spell is about as good as it gets for a pacifist elemental mage, as it enables you to become completely invisible for a period of time. To make the most of it, you'll probably want to invest skill and/or attribute points beyond the bare minimums required to learn and cast Invisibility though, because it has a short duration of 3 turns per casting level. However, even a few turns of invisibility can be valuable at key "pacifist challenge" points, like making a quick dash into a patch of torchlight to loot an enemy treasure chest in a chamber surrounded by dangerous enemies.
Portal: This spell could be considered a luxury, but it was one of our very favorites and enables you to very efficiently move between zones. Note: You have to set an anchor point for each teleportation in order to use it and it usually (perhaps always) only works outdoors, but is very convenient if you have ambitions to amass a fortune in gold by visiting numerous merchants with less time-consuming legwork. You can even teleport yourself directly back and forth between areas that are so far apart that quick-traveling is impossible (e.g. Durnore in the far north, and Picaroon Isle in the far south).
Abyssal Freeze & Ice Lance: These two spells will blast an enemy with different types of freezing damage. We never learned them, but were never sorry to find scrolls for them in enemy treasure chests either, since these and other high level spell scrolls tend to be worth a lot of gold.
Supernova: Same as the two above, except it will blast enemies with fire damage.
Divination Magick: Tier 1
Divination magick skill required: 1
Minimum wisdom required to cast spells: 15
Divine Heal: This spell enables you to restore your hit points just by casting it, and combined with a solid Perception score, can save you a good amount of gold by removing reliance on healing potions if you find yourself taking a lot of damage.
Entangle: This causes entangling vines to rise up and ensnare a target so that they can't move for awhile, but without harming them. This can be a lot of fun on a pacifist run, but we found it often wouldn't work on higher-level enemies even at a high casting level (whereas the elemental Sparkling Wonder spell almost always worked for at least a few turns on the same enemies).
Create Food: Casting this enables you to create small edible food items like seeds or berries. While we didn't use it much, it's an asset for not only saving gold from not having to buy food, but also earning gold, since the items (like Bittercup Seeds or Yambi Berries) can be sold to merchants. (Note that both the Create Food spell and the Foraging skill were modified in Book III so that they weren't "secret weapons" for earning as much gold as you wanted.)
Leatherskin: This increases your armor rating and reduces damage you take, so is prospectively useful on a pacifist run if you're having trouble with taking too much damage.
Cat's Eyes: This is more prospectively useful than the Predator Sight elemental spell, since it gives you cat-like vision enabling you to see more clearly in the dark (rather than just causing only the enemies to glow green in your own vision, leaving the surrounding area dark).
Lore: This spell identifies unknown objects, so that you can find out exactly what they are (and how much gold they're actually worth). A mild caveat is that Lore usually requires a much higher wisdom score and casting level (and therefore also a higher Divination level) to identify the more valuable objects, so it might take awhile to be able to use it effectively. However, it's a great spell to have either way.
Note: If you don't identify an object in Eschalon yourself, you'd have to pay a merchant a fairly hefty price to identify it for you, which would waste a lot of gold. (And if you don't identify items but still try to sell them, all the merchants in the game will tell you that the item "isn't worth much" to them, and then make a lowball offer of only a fraction of the item's actual worth.)
Detox: This removes poisons from your bloodstream. Poisons usually weren't all that dangerous to us in pacifist runs through the Eschalon trilogy since they'll be automatically purged from your bloodstream after some time passes, but it certainly doesn't hurt to learn this once anyway. (Also: If you play with some of the more strict difficulty options turned on, then it's impossible to save your game if you're poisoned, so this could make a bigger difference in that case.)
Bless: This spell sounds wholesome, but as far as we know it's actually not useful on a pacifist run, since it boosts your to-hit and maximum damage, but not your strength. (But there is also a Divination spell "Ogre Strength" described below, which will increase your strength radically, so you can carry away more treasures even if you have a low or modest strength score.)
Fleshboil: This is a ranged attack spell that we never learned or used on our pacifist runs, but you can always still sell unwanted scrolls for gold.
Divination Magick: Tier 2
Divination magick skill required: 5
Minimum wisdom required to cast spells: 20
Haste: This powerful pacifist run asset enables you to move with increased speed, so that you can do twice as many things per turn as most enemies. This will usually make it very easy to run away and leave most enemies in the dust, which is very convenient in many places throughout the game. In some of the more dangerous places later on, it can be a lifesaver when you're being pursued by dangerous fast-moving foes who can attack from a distance, such as Taurax spearmen who are only susceptible to Sparkling Wonder for 1-2 turns, and are immune to spells like Entangle.
Ogre Strength: This temporarily increases your strength, which isn't only of interest to warriors, but also for pacifist challengers determined to escape major dungeons while loaded down with enemy treasure. If you get your hands on this spell and/or Potions of Ogre Strength that do the same thing, you can save a lot of attribute points that you might otherwise be tempted to use to boost your natural strength score.
Nimbleness: This spell temporarily increases your dexterity score in proportion to the casting level. This could sometimes be a valuable spell to improve your rate of success with picking locks (which is directly impacted by your dexterity score, as well as your level of lockpicking skill).
Stoneskin: This causes your skin to be come hardened and increase your armor rating and damage reduction, which can obviously be useful if you were having a problem being slain by tough foes.
Turn Undead: This causes undead creatures to be repulsed by you and run away, which can make it like a powerful variant of the Sparkling Wonder spell, but which only works on undead. (It will inflict at least a few points of damage on the undead you cast it on, but we never saw it actually destroy any. But if you want to win a zero kill run and also inflict zero damage points, you won't ever be forced to rely on it.)
Cure ailments: This will cure serious afflictions like diseases (which you can sometimes contract from traps even if you do a good job of keeping enemies at a distance). Diseases vary, but some of them can cause significant impairments to your abilities until you either drink a disease-curing potion (which cost a lot of gold), or cast this spell.
Protection from Curses: This surrounds you with a divine aura to protect you from the effects of cursing, which are often very vexing in the same way as the worst diseases, since they can significantly impair your abilities until you either cast de-hex yourself with the tier 3 Divination spell, or travel all the way to a priest and pay a hefty sum of gold to have them remove the curse.
Charm: Whether to learn this depends on your pacifist run scruples: We didn't use it, but it will temporarily make an enemy bewitched and attack any other creatures that are aggressive toward you. (If you want to prevent deaths from other beings attacking each other, it's obviously a lot better to use Sparkling Wonder to make them run away, or Entangle, if they're not too high-level for the latter spell to work.)
Sunder Flesh: This dire attack spell is something we never learned or used, but only sold for gold.
Divination Magick: Tier 3
Divination magick skill required: 11
Minimum wisdom required to cast spells: 25
Dehex: This will remove any hexes or curses, so is definitely the most valuable of the tier 3 spells on a pacifist run if you happen to be afflicted with a curse. (This is a fairly rare danger, however.)
Mystic Hammer: This evokes a hammer of divine energy to crush opponents.
Mass Boil: This is another attack spell we never tried, and just sold these scrolls for gold.
This rather rare Divination spell can be fun to temporarily summon different kinds of creatures (like rats, slimes, wolves or spiders), and cause the creatures you summon to follow you around for awhile on the same map where you cast the spell. It seems to be a very rare spell that only occasionally turns up in high-end magick shops like Luci's "Darkest Arts" in Port Kuudad, but it isn't really useful on any soft-hearted pacifist run in which you don't want to cause the death of either your summoned creature, or any other enemies that might attack the two of you. (While not a tactical necessity, it was still fun to summon a Catacomb Rat in an empty meadow with no enemies nearby, however. Trying to talk to the summoned rat while it sat quietly in the grass also produced the message "This person just ignores you. Perhaps they are too busy to chat.")
Elemental vs Divination Magick on a Pacifist Run:
While Elemental magick was our discipline of choice, you won't be forced to use only one discipline, since you can train both up to level 8 from Luci at Port Kuudad, add more points with a skill manual, and find special items like amulets and wizard hats that can increase the skills even further. Unlocking at least the tier 2 Divination magick spells is a great idea since it will let you use caste Haste and Ogre Strength.
However, on a pacifist run, we preferred not to invest the extra skill and attribute points required for tier 3 Divination (i.e. an extra 6 skill points to hit level 11 Divination, and extra 5 attribute points to hit level 25 wisdom), since none of the Tier 3 Divination spells are actually very useful on a pacifist run. (The only one that was potentially useful was possibly Dehex, which is never a necessity if you're cautious around enemies that can curse you.)
Elemental, on the other hand, is well worth learning beyond the level 8 training maximum. As far as we know there is no alchemical equivalent to the Sparkling Wonder spell that you can brew, and the Dense Nimbus spell is the best defense against projectiles we found. Also, while you can brew Invisibility potoins with high level alchemy skills, the required reagent ectoplasm is relatively scarce, but an Elemental mage can cast invisibility as many times as their mana allows once they meet the minimum requirements to learn the spell. The Portal spell, while not required, is also very nice to use, and will require higher level Elemental.