Night-Walker, Headless

If you would lose unspent mana, that mana becomes
black instead.

At the beginning of your precombat main phase,
look at the top card of your library. You may reveal
that card if it has three or more colored mana
symbols in its mana cost. If you do, add three mana
in any combination of its colors and put it into your
hand. If you don't reveal it, put it into your hand.