Omnath, Locus of All

If you would lose unspend mana, that mana
becomes blask 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.