Shroud of Kruphix

Whenever a creature you control with hexproof deals combat damage to an opponent, you may put that creature on the bottom of your library. If you do, draw two cards, and add X mana in any combination of colors to your mana pool, where X is that creature's converted mana cost.
Until end of turn, this mana doesn't empty from your mana pool as steps and phases end.
{1}{g}{u},{t}: Target creature you control gains hexproof and is unblockable until end of turn.