Kana Asuga, Keeper of Lotus

Ninjutsu {u}{b}{g}({u}{b}{g}, return an unblocked attacker you control to hand: Put this card onto
the battlefield from your hand tapped and
attacking.)
When Kana Asuga deals combat damage to a player, add that much mana in any combination of {u}, {b}, or {g}. Until end of
turn, mana doesn't empty from your mana
pool as steps and phases end.