D/D/D Stone King Darius (Rare)

2 Level 3 Fiend-Type monsters
Once per turn, during either player's turn: You can detach 1 Xyz Material from this card, then target 1 Dark Contract card you control; destroy it, and if you do, draw 1 card. If this card battles an opponent's monster, during damage calculation: You can detach 1 Xyz Material from this card; make this card unable to be destroyed by that battle, destroy the opponent's monster that battled it after damage calculation, and if you do, inflict 500 damage to your opponent.