Mecha-King Ghidorah

Flying
Whenever you cast a spell, put a +1/+1 counter on Mecha-King Ghidorah for each of that spell's colors.
Remove five +1/+1 counters from Ghidorah:
Add {w}{w}{u}{u}{b}{b}{r}{r}{g}{g} to your mana pool. Activate this ability only once each turn.