Rhiannon

Pay 5 life: Put a wealth counter on Rhiannon
(if you have a creature with 10 or more wealth counters on it, you win the game)
Pay 1 life: target creature gains +1+1 and lifelink
until end of turn
{t} Target creature gets -3-3 and unblockable
Pay 2 life: Untap all permanents you control