Mask of Brutality is a Equip Spell Card.
Spell Cards are usually activated from the hand on your turn unless their type gives another timing window.
On the current TCG and OCG Forbidden & Limited lists tracked here, Mask of Brutality is Unlimited.
YGOPRODeck lists Mask of Brutality for these formats: GOAT, OCG GOAT, Duel Links, Speed Duel, Common Charity, Edison, TCG, OCG, Master Duel.
Mask of Brutality belongs to the Mask archetype—use that tag when searching for engine pieces and tech options.
A listed print of Mask of Brutality appears in Battle Pack 3: Monster League (BP03-EN137) at Common rarity.
Among markets shown on this page, the lowest listed snapshot for Mask of Brutality is about $0.12 on Cardmarket (prices change frequently).
