Sedge Sliver

All Sliver creatures have "This creature gets +1/+1 as long as you control a Swamp."

All Slivers have ": Regenerate this permanent." (The next time it would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

Their flesh is as sodden as the fens in which they live, oozing to fill any wound and squishing to absorb any blow.