The High Elven Archmages are amongst the greatest practitioners of Magic within the mortal realms. Through decades, and often centuries, of painstaking research and scrupulous study, they learn to master magic in its purest form, an art known simply as High Magic. Those who mastered this most challenging of lores hold the entire spectrum of magic at their command.
At a High Mage's word, shimmering fields of magical energy spring into being to protect his allies, and the fires of courage blaze anew within their hearts. The truly gifted can even becalm the Winds of Magic themselves, collapsing a raging tempest until naught but a gentle breeze remains. Yet it should not be thought that High Magic is reserved for defensive means alone. With but a wave of his hand, a High Mage can call down the wrath of the heavens, paralyze his foes, or immolate whole regiments with Asuryan's fire.
It is little wonder then, that in times of strife, the Phoenix King will beseech the Tower of Hoeth for aid. The Loremasters of Saphery never shirk from their duty, for they know that their gifts stand between Ulthuan and annihilation. Traditionally, mages fulfil an advisory capacity in addition to their battlefield roles, lending an insight that transcends mortal comprehension. Such knowledge has even led to mages being given command of whole armies, a state of affairs that is especially common when Ulthuan is beset by supernatural threats from the Realm of Chaos.
The Lore of Fire is the go-to damage lore for many factions, and High Elves can access it as well. It provides the ever-efficient Burning Head, Fireball, and Firestorm damage spells for different situations, but also the potent Kindleflame passive which buffs all fire attacks in your armies for 15 seconds (and the High Elves have many flaming attacks, including Fire and Arcane Phoenixes as well as Sun Dragons, both their special abilities and normal attacks, as well as Lords with the Incendiary trait, Banner of the Eternal Flame, RoR Archers, etc).
Consider whether you want your army to have a single caster (the Archmage) or two (the Archmage and a Mage hero). If you go for two casters, strongly consider taking Fire on the hero mage instead of the Archmage. The Lore of Fire hero mage is the only one who can mount a dragon, this allows your army to have two dragon-mounted casters.