Rosaria’s Fingers is a covenant that can be joined by speaking with Rosaria in the upper levels of Cathedral of the Deep. To reach her, take the elevator behind one of the shortcuts to the Cleansing Chapel and make your way through the rafters.
WARNING: Joining will end Sirris of the Sunless Realms quest line.
A PVP covenant, Rosaria’s Fingers can invade worlds with a Red Eye Orb or be summoned with a Red Sign Soapstone.
Defeating a Host of Embers or a Blue Phantom will result in a Pale Tongue, which can be turned into Rosaria in Cathedral of the Deep.