Might Makes Right

2014-07-18 Gaining control of a creature doesn't cause you to gain control of any Auras or Equipment attached to it.
2014-07-18 The ability can target any creature an opponent controls, not just one that's tapped.
2014-07-18 The ability will check its condition again as it tries to resolve. If, at that time, another player controls a creature with the greatest power or tied for the greatest power, the ability won't do anything.
2014-07-18 The ability will trigger only if you control each creature on the battlefield with the greatest power as the beginning of combat step begins. If another player controls a creature with the greatest power or tied for the greatest power at that time, the ability won't trigger at all.
2014-07-18 "Each creature on the battlefield with the greatest power" may be a single creature if each other creature has less power.

Card is in preconstructed decks:

mtg.wtf