Spells I've seen (I think this is all so far but could be wrong):
Revive Land
Teleport (you and your army back to your lands)
Mass Heal (you and all units in your army)
Imbue Champion (use your essence to improve a Champion's magical power)
Summon Fire Giant (which looks suspiciously like a troll 
)
Charm Monster (to join you)
Raise Land
Lower Land
Create Desert
Create Forest
Create Hills
Create Swamp
Spells are bought with spell points, and require knowing a particular spell 'book' (fire, for example). Some spells require a shard. Charm monster, for example, is from the 'basic' spell book (at least that's what the description says, I haven't checked to confirm), costs 100 spell points to purchase, requires 1 air shard and 10 mana to cast.
