Vallyre, Youthful Dreamer

Whenever you cast a spell, add {r}{r}. Until end
of turn, you do not lose this mana as steps and
phases end.
If there is unspent mana in your mana pool at the beginning of your end step, empty your mana
pool and Vallyre deals that much damage to an opponent.
"How can you not know this one? It's a classic!"