Defender

{w}{u}{b}{r}, {t}: Transform The Core. Then if there is not a legendary creature with {u}{u} in its mana cost on the battlefiled, search your library or hand for one and put it onto the battlefield, then shuffle.

Enchant legendary creature with two {u} in it's mana cost

You control enchanted creature

Enchanted creature gets +1/+0 for each creature your opponents control, gets +0/+1 for each creature you control, has menace, and is an artifact and your commander in addition to it's other types.