Shaman Rage

[Droxx]

Frenzy
Decrease Mana from 19 (L19) to 40 (L60)
Increase Strength from 19 (L19) to 30 (L60)
Increase Armor Class (AC) from 7 (L19) to 11 (L40)
Increase Hit Points (HP) from 5 (L19) to 14 (L60)

Fury
Decrease Mana from 39 (L34) to 65 (L60)
Increase Strength from 27 (L34) to 40 (L60)
Increase Armor Class (AC) from 13 (L34) to 17 (L60)
Increase Hit Points (HP) from 10 (L34) to 17 (L60)

Rage
Decrease Mana from 103 (L49) to 125 (L60)
Increase Strength from 50 (L49) to 61 (L60)
Increase Armor Class (AC) from 18 (L49) to 20 (L60)
Increase Hit Points (HP) from 26 (L49) to 32 (L60)

Voice of the Berserker
Decrease Mana from 64 (L59) to 65 (L60)
Increase Strength from 74 (L59) to 75 (L60)
Increase Armor Class (AC) from 28 (L59) to 29 (L60)
Increase Hit Points (HP) from 34 (L59) to 35 (L60)

Although there's no mana reduction here for some reason. So its pretty much the most powerful spell in the game.