Pirates of the Eldritch Sea - DnD 5e
Balinor's Cursed Dagger
A black, broken, obsidian dagger
Reaching out psychically to the creature comprised of shadow, the creature reached back, seeping into his mind, leaving no trace of him behind, but the broken dagger in the center of the room.
Upon attempting to release the water elemental after recovering. The elemental immediately encased him in water, attempting to drown him. The shadow creature reached out, and then choked the life out of the elemental, leaving it unconscious on the ground.
The following game session, the dagger seemed to take control of Balinor, demanding the blood of a surrendered dwarf. Balinor then slit the dwarves throat.
See: sessions 6 and 7 for details