Klauth, Unrivaled Ancient AFC-50/5075 (The List Reprints)

Flying, haste Whenever Klauth attacks, add X mana in any combination of colors, where X is the total power of attacking creatures. Spend this mana only to cast spells. Until end of turn, you don't lose this mana as steps and phases end.

NM - $18.50
LP - $14.50
MP - $11.00
HP - $7.50
DMG - $4.00