Existing in the center of the Citadel Vigilant, itself inside a massive near-impenetrable storm known as the Vhulian Swirl, the weapon was lost to Imperial records but during the War of Beasts was eventually captured by a band of Fallen under the Librarian Osandus. The weapon did not fire projectiles, instead forcing a breach in space-time to bring a beam of crushing energy upon a single point. This energy opened up a minuscule singularity that could bypass all types of force fields and barriers, unleashing a devastating wave similar to the effect of a Black Hole.
During the War of Beasts, Abaddon himself journeyed to the Citadel Vigilant to claim the power of the Voidclaw in a bid to reshape the Nachmund Gauntlet. He fired the Voidclaw between Vigilus and its moon, creating a devastating wave of gravitic force that became known as the Vhulian Anomaly.