{T}: Add {C}. {T}: Add one mana of any color. Spend this mana only to cast an Assassin spell or a spell that has freerunning, or to activate an ability of an Assassin source.
"Monteriggioni will outlast her enemies." —Mario Auditore
2024-07-05
You can use the mana produced by Brotherhood Headquarters's last ability to cast a spell with freerunning even if you're not paying that spell's freerunning cost.
2024-07-05
"Assassin sources" include any objects with the Assassin creature type. This means you could spend the mana to activate an ability of a permanent with changeling (a keyword ability that gives it all creature types) or an Assassin card in your hand or graveyard, for example.