Hurkalex, Pit Tyrant

: As long as it's your turn, Hurkalex, Pit Tyrant is a 5/5 Dragon creature with flying and first strike that's still a planeswalker.
-X: Until end of turn, whenever a creature blocks, Hurkalex, Pit Tyrant deals X damage to that creature. Put a loyalty counter on Hurkalex.
: Hurkalex, Pit Tyrant can be your commander.