Komainu Battle Armor is a rare Artifact Creature — Equipment Dog card from The List (PLST), collector number NEC-21. Current market price: $3.90, TCGplayer market prices via Scryfall.
Menace Equipped creature gets +2/+2 and has menace. Whenever this creature or equipped creature deals combat damage to a player, goad each creature that player controls. Reconfigure {4} ({4}: Attach to target creature you control; or unattach from a creature. Reconfigure only as a sorcery. While attached, this isn't a creature.)