Flaming Corpse's Deep Elf Air Elementalist/Summoner/Necromancer guide
This guide details a progression through a set of skills well-suited to Deep Elf Air Elementalists. Other races with similar aptitudes can also follow this path, as can other backgrounds (such as Wizards, other types of elementalists).
The overall progression outlined here involves heavy use of air magic in the early game, which enables the use of Summon (air) Elemental by the midgame, then a heavy concentration on Necromancy until Necromutation can be consistently cast, at which point Haunt becomes the primary means of offense.
Your starting spellbook will determine what tactics you must employ at the beginning of the game, as well as which spell schools you can train. Deep Elves, with their poor fighting aptitude and low HP, must generally kill foes from afar.
Your earliest focus should be on Spellcasting, Conjurations, and Air Magic. A few levels of Charms are sufficient to reliably cast Swiftness; additional training should be done later to be able to cast Haste and Deflect Missiles. You also want a few levels of Translocations to get Blink up to Excellent after you learn it.
Deep Elves are frail, and poor fighters, and are thus best kept out of melee. They are, however, capable users of Short Blades, and are quite proficient at stabbing. When confused, monsters cannot effectively fight back, and are highly vulnerable to stabbing. This makes the combination of Mephitic Cloud and daggers worthwhile for Deep Elves, though avoiding melee altogether is a safer strategy. Stabbing also combines modestly well with a summoning strategy, as "distracted" monsters are easier to stab, though not as much as confused monsters.
Even if you do not plan to engage in much melee, Fighting skill does offer a modest but important boost to your HP.
Deep Elves' proficiency with short blades and stabbing makes daggers the best choice for them. A dagger of venom is a good choice, as is one with the Electrocution brand. Quick blades are also a good choice. It is useful to carry an extra blade with the holy wrath brand to use against undead. And weapons with the draining brand may be the best "defensive" weapon in the early game, as they tend to kill weak monsters quickly by lowering their hit dice, at the cost of reduced XP for the kill. Which is reported to be minimal. Much lower than allowing summons to kill for you.
Daggers have one problem, they have a very low base damage. In the later game their damage output each turn is way to low to do any serious damage. You should either rely on stabbing damage (confuse, sleep, etc the monsters first, or be invisible), or ditch the daggers completely. In most cases the xp penalty of increasing the daggers to minimal delay isn't worth the effort.
The best brands on low damage weapons are those that do not multiply the base damage (such as Vorpal or Flaming do). Aim for draining, Electrocution, Venom, and even Distortion. Antimagic also has situational uses (Wield it when out of magic and face to face with the enemy caster).
If you do not plan to engage in much melee, a magical staff is a better choice -- Wizardry if some of your spells have a low success rate, Power for the extra MP, or Channeling if you do not have Sif Muna's channeling ability.
A rod is also a good choice, if you can find one. A Rod of Smiting pairs up well with summoning tactics, since it will not harm your allies. A Rod of Demonology may allow you to omit Abjuration and Recall from your list, and cast supplemental summoning spells.
Training a couple of levels of Armour skill is useful for reducing the spellcasting penalty for using heavy armours. It is not reduced by much, however -- spellcasters should generally stick to robes, leather, troll, or mottled dragon armour. With more armour skill they can get away with ring mail or swamp dragon armour, or possibly elven scale mail. With luck, you may find a light artefact armour with several good resistances or other enchantments.
Shields and large shields should be avoided, but if your spell success rates are high, you can usually get away with using a buckler, especially an elven one. A buckler of reflection is nice, a buckler of protection better still -- if you can find one.
An amulet of the gourmand is quite useful in the early game, when food is tight. Spellcasters have greater food requirements than other character types due to spell hunger, and a great way to combat this is to be engorged as often as possible. Having lots of food also lets you aggressively channel energy, although the spell Sublimation of Blood is a good alternative for turning chunks into mana.
Conventional wisdom would suggest that an amulet of guardian spirit is disastrous for spellcasters. However, Deep Elves top out at 124 HP at level 27 (135 with a few levels of Fighting), making them vulnerable to one-shot kills from Lehudib's Crystal Spear and similar dangers. With maxed spellcasting an amulet of the guardian spirit adds 50 more HP in the form of MP that can be healed rapidly by channeling energy or using Sublimation of Blood. While this amulet puts you in danger of losing all your MP from a hard hit, this is still preferable to losing all your HP.
A ring of teleport control is highly recommended in combination with the spell blink as a high-reliability means of escape, and to avoid getting surrounded by several dangerous enemies when stumbling upon teleport traps.
A ring of magical power is one of the best choices of rings for aggressive spellcasters; when combined with an amulet of the guardian spirit, it also translates into an effective 9 extra HP.
Resist the temptation to carry lots of spellbooks around with you, as they weigh 7 aum each. Carry the spellbook you'll be memorizing your next spell from, a handful of emergency-use potions, and a couple of rations or other food. Put everything else in your stash.
Spellcasters have limited need for wands, which weigh 10 aum each. A wand of teleportation or healing are good for emergencies, if you can find them; any conjuration-type wand is also good against dangerous enemies in the early game.
Sif Muna is the obvious choice for this character path; Deep Elves' proficiency in all spell schools makes the variety of spell books gifted by Sif quite valuable. Channel energy is also an excellent ability for an aggressive spellcaster, although a Staff of Channeling can substitute for it.
Unfortunately, the spell Necromutation -- which is central to the Summoner/Necromancer portion of this character guide -- is rarely found outside the Necronomicon, which Sif Muna does not grant. The Necronomicon can often be found in the dungeon, a shop, or in one of Sif's artifact books... but the only guaranteed way of getting it is to worship Kikubaaqudgha. Kiku's corpse-granting ability also serves as an alternative to energy channeling when combined with Sublimation of Blood, making Kiku a plausible alternative to Sif.
Vehumet is also a good choice, especially to acquire Mephitic Cloud early via a Book of Conjurations gift. Switching from Sif to Vehumet in the late game is also worth considering (once all desired spells have been gained from Sif's gifts); Vehumet boosts the power of conjurations and summonings and grants MP from killing monsters, making him more potent in dangerous settings such as Ziggurats.
Put all your stat increases into Strength until you get it up to at least 8, so that you are not encumbered all the time. If you find a strength-granting artefact, you might be able to get away with less, but watch out for stat drains. Later you will have Flight and Necromutation, which will bring your carrying capacity up to about 500 aum.
Put the remaining increases into Intelligence.
Changing levels (i.e., going down a stairwell) is one of the most dangerous times for your character. You might find yourself planted right next to a superdangerous unique, who might take the opportunity to swat at you while you climb back up, then follow you upstairs to finish you off. Therefore, whenever taking a set of stairs for the first time (down or up), you should cast all the best charms on yourself that you can beforehand, and surround yourself with summoned allies that can keep your enemies distracted and distant. You can only take allies with you that are immediately next to you when you change levels. This limits you to eight allies, or fewer if there are walls next to the stairs. Take as many as you can.
Recall is good for engaging monsters that are around corners; if you have several summoned allies somewhere on the level, they will surround you and extend past the corner, where they will engage the monster. Summoning new monsters can have the same effect -- especially Summon Elemental, which allows you to summon in a specific direction.
Don't forget to 't'alk to your allies; even mindless ones will understand a command to attack. Without that command, most will cluster around you, doing nothing.
The lower-level summoning spells are not that useful, although Summon Butterflies is a fantastic means of escape; it instantly surrounds you with a two-tile deep cloud of butterflies which will get out of your way but not your attackers. The butterflies also interfere with ranged attacks, providing cover while you back away from a centaur or spellcaster. It's also a great means of finding teleport or zot traps on the lower levels; summon up a cloud, then watch them flutter around a room and see if they hit anything (However, they will not set off dart, blade, alarm, etc. traps, or discover shafts, being flying creatures).
In a pinch, Summon Small Mammals can protect you in a similar manner; at the very least, they are good for blocking your enemies as you retreat through a corridor.
Summon Elemental is an excellent mid-game summoning spell. The type of elemental you summon depends on what type of tile is in the direction of your summon. An empty tile will produce an air elemental; a rock (not stone) tile will produce an earth elemental; lava or smoke will produce a fire elemental; and water will produce a water elemental.
Fire elementals are weak. Water elementals are good but require a nearby water source. Air elementals are durable, hit hard, and are incredibly fast. A swarm of five or more can overcome just about any mid-game enemy. Being flying creatures, they are useful in any dungeon branch, such as The Shoals or The Swamp, and as an additional bonus, they're fast enough to keep up with you even when you're swift, flying, and hasted.
The biggest drawback is that you want to have a skill of 15 in Air Magic in order to summon friendly air elementals. Deep Elf Air Elementalists can usually achieve this by experience level 10 to 15, at which point they can conjure armies of air elementals. Air elementals are immune to electricity, which means you can fire Shock and Lightning Bolt through them with impunity. Airstrike, another Air spell, is also great in combination with summons; its smite targeting allows you to avoid hitting your allies. Be careful to not summon air elementals if you do not have a means to defeat them, as you cannot outrun them, and they do hit quite hard. You may be able to get away using haste, Summon Butterflies, and a nearby stairwell. As of 0.9, Airstrike is useless against renegade air elementals.
An air elemental fan is a good way to generate lots of elementals without depleting your MP (you can, for instance, use it while waiting for your MP to recover). You must have about 5 levels of evocations before it is useful, as even at that level you will still fail to use it more than 90% of the time.
Earth elementals are also good companions; they are slow but hit very hard. Summoning an earth elemental is also a fast way to dig through a single rock (not stone) wall. You only need to have 5 levels of Earth Magic skill to maximize your chance of getting a friendly one (and they are easy to run away from anyway). However, earth magic is the opposite element from air magic, which means earth magic will train very slowly if you already have a lot of skill with air magic (and vice versa).
Haunt is the unholy grail of summoning spells. It is the only summoning spell in the game that uses smite targeting: instead of surrounding you with summoned monsters, it surrounds your opponent with them. After 3-5 castings, an opponent is likely to be completely surrounded by nefarious spirits, and quite distracted as a result.
It comes with several drawbacks: casting it can make you sick; it has a high mana cost (7); and a high spell hunger cost. All of these drawbacks are almost completely negated by using Haunt in concert with Necromutation. In lich form, you cannot get sick and do not experience hunger from any source -- which means you can cast Haunt five to eight times in a row, channel energy repeatedly, and repeat the process every couple dozen turns or so. Few opponents will have any chance of resisting such an onslaught.
Shadow Creatures will summon a single "random encounter" appropriate to the level you are on. On levels that have a mix of weak and dangerous monsters, this may or may not be useful. On D:10, for instance, you can get a large band of ogres, including an ogre mage... or you can get a single hobgoblin. In the Realm of Zot, where every monster is dangerous, it is extremely useful, despite the occasional moth of wrath.
Summon Horrible Things
Summon Horrible Things is useful on levels that are home to weak "random" encounters but very strong special encounters, such as The Tomb or the last level of The Vaults. Shadow Creatures is not useful on such levels, and Haunt's progeny may struggle to take down guardian mummies or large numbers of dragons.
Late Game Skills
Most of the focus on necromancy in this character path involves two spells only: Necromutation and Haunt. To cast these spells effectively, you should have 15+ Necromancy and Transmutations skills (for Necromutation) and 15+ Necromancy and 10+ Summonings (for Haunt).
A modest amount of Invocations skill is desirable once you start using channel energy, and using channel energy is the best way to train it. Note that the only important skill levels here are the multiples of 4; you will get more mana per use at skill 4, 8, 12, and so on. Just 4 levels will let you recover your mana quickly in between fights, more will let you do so faster, perhaps even during the fight.
Spellcasting should be trained all the way up to level 27. It influences your MP, the number of spells you can memorise, and your spell success. Deep Elves, with +4 proficiency at spellcasting, can reach 27 by the time they get to Zot:5.
Conjurations will cease to be important once you switch to a summoning-heavy strategy. You can usually turn it off once you've got Haunt mastered. Before then, though, Orb of Destruction is very, very useful against several dangerous uniques.
Getting Air Magic up to about level 20 will allow you to cast Tornado, one of the most fearsome offensive spells in the game. As a bonus, air elementals are immune to its damage, making summoning and tornadoes an excellent one-two punch.