Oblivion Shell of the Maw

A massive 12.7 x 55mm cartridge with a casing forged from cold-iron dipped in liquid shadow. The projectile is not solid metal, but rather a pressurized capsule of viscous, ink-black void matter that pulses with a rhythmic, heartbeat-like vibration. Faint, agonized whispers emanate from the lead when held to the ear.