Spell Casters can be :
1-Cleric : High Elven Unit, one of his abilties is heal.
2-Blood Seeker : Blood Elven Unit, one of his abilties is to give the friendly units a buff to make them drain the enemy's hit points
i don't know the third
and you can add Agility Hero called Nightwolf (Yeah, that's right MK fans, Nightwolf)
a Night Elven Hero his ultimate is to turn into a wolf with high speed and strong attack and roar ability