Kalista, Spear of Vengeance

Kalista can't be blocked by creatures with power 3
or less.

Level up (When 3 or more other allies die while Kalista is on the field, give her +1/+1 and "When Kalista attacks, return the strongest creature in your graveyard to the battlefield tapped and attacking. All damage Kalista would take, the revived creature takes instead. Destroy the creature after combat resolves.")