From The Heroes of Might and Magic III wiki

Class	Earth Magic
Basic cost	30
Duration	Instant
Level	5th

Damages target enemy stack

Level	Effect
None	Damage is (Spell Power *75 +100)
Basic	Cost reduced by 5
Advanced	Damage is (Spell Power *75 +200)
Expert	Damage is (Spell Power *75 +300)

[edit] Comments

Single most powerful targeted damage spell in the entire game. Its damage scaling is vicious, and it can easily annihilate even the most resilient of enemies (excluding the higher-level Golems, even if you had Power 99 and Orb of Silt).