Swaaamp, Reluctant King

Lifelink, Menace.

Sneak attack - As long as Swaaamp, Reluctant King is attacking with another legendary creature, it has Double Strike.

{3}{b} Sacrifice a swamp. Swaaamp, Reluctant King gains X power until end of turn, where X is the number of swamps in the battlefield.

Don't split the party (You can have four commanders if they all have Don't split the party.)