Find and clear out challenge room (see image). Enemies will drop weapons. Equip one with a locked trait and leave the room. Walk far (at least 4 rooms length) away and go back. Enemies will respawn. Kill until a spawn of Anomos is left. Don't destroy the Abyssal Trichozoid (spawner). Unlock traits by killing Anomos. Level up all weapons in the room then clear it. Leave and repeat the process.