Karn, Legacy Reforged (Retro) [March of the Machine: The Aftermath] Equipment Xantcha attacks each combat if

Xantcha attacks each combat if able and can't attack its owner or planeswalkers its owner controls

This is different from sieges

and anything else not from the MOM main set

−3: Nicol Bolas

−3: You draw X cards and Commodore Guff deals X damage to each opponent

Karn, Legacy Reforged (Retro) [March of the Machine: The Aftermath] Equipment Xantcha attacks each combat ifSet: March of the Machine: The Aftermath Type: Legendary Artifact Creature Golem Rarity: Mythic Cost: {5} Karn, Legacy Reforged's power and toughness are each equal to the greatest mana value among artifacts you control. At the beginning of your upkeep, add C for each artifact you control. This mana can't be spent to cast nonartifact spells. Until end of turn, you don't lose this mana as steps and phases end.