Cairn, Unchained at Last

At the beginning of combat on each of your opponents turns, you may pay {w}{r/g}, if you do, choose a creature that player controls. It must attack you if able, and must be blocked by Cairn if able. Cairn gains +0/+X until end of turn, where X is the chosen creature's power.

Metamagic — {3}: If {r} was spent, Cairn gains +1/+0 and menace; if {g} was spent, Cairn fights up to one target creature; if {w} was spent, Cairn gains +0/+1 and vigilance; if {u} was spent, Cairn gains hexproof. These effec