Blade of the Oni is a mythic Artifact Creature — Equipment Demon card from Magic Online Promos (PRM), collector number 97979.
Menace Equipped creature has base power and toughness 5/5, has menace, and is a black Demon in addition to its other colors and types. Reconfigure {2}{B}{B} ({2}{B}{B}: Attach to target creature you control; or unattach from a creature. Reconfigure only as a sorcery. While attached, this isn't a creature.)