Harvester

Aura of Corrosion reduces your attack and magic damage based on total amount of damage you have dealt to the unit so far.
Cloud of Death may kill some of your units instantly. Chance of being killed grows with total amount of damage you have dealt to the unit so far!
Unit's anger causes splash damage which hits every single member of your army. Rising total damage dealt to unit makes Explosion of Anger hits stronger than before!
Their sheer size towering over even the mightiest of Hellbrutes, the only purpose of these juggernauts is to circle the worlds of Emporea and collect as many Tears as possible. Their origin is unknown, but the strong odour of burnt mana that accompanies them suggests a magical, outworldly realm.
"Would you look at the size of that thing! I'll bet you five gems I can tame this handsome fellow!"
Grahg Irontooth, winner of this year's Behemoth Taming Championship