from Mallorca myself, still no idea wha "cosca" means, unless that you're familiar with spanish expressions (and i doubt it) "cosca" is generic for payin attention/understanding, pretty much in VERY informal chatter. But i see you're looking for a sort of mafia, i could suggest you something like "Mafia Gallega" or something likewise. As acually the faction name, no offense intended, makes no sense at all.
Seeing that there's someone fron Galicia, i also suggest you to ask him (and take note) from expressions from that region such "Carallo!"
oh, and don't let you fellows spout gringo... that has nothing to do with spanish