Long before the 22nd century, the indigenous inhabitants of Altamid engineered the Abronath as a weapon of war. However, as they could not control it, they split the weapon in two and launched the pieces into space, hoping they would never be found. The Ancient Ones later abandoned their homeworld, leaving their technology behind.
Krall, the former captain of the Federation starship USS Franklin that had crashed on Altamid in 2164, sought the Abronath as the instrument of his vengeance on the Federation. He managed to locate one piece after lifetimes of searching.
The other piece of the Abronath came into the possession of the Fibonans. In 2263, the Fibonans passed the artifact to the Federation to be presented as an offering of peace to the Teenaxi. Mistrustful of the Fibonans and suspicious of the inactive weapon, the Teenaxi refused to accept the Abronath piece, and Captain James T. Kirk thereafter had it stored in the archive vault aboard the USS Enterprise.
Using captured Magellan probes to access the Starbase Yorktown database, Krall discovered the location of the second piece. He dispatched Kalara to lure the Enterprise to Altamid, where his forces destroyed the Enterprise and captured most of its crew. Kirk had given the Abronath piece to Ensign Syl for safekeeping, but Krall coerced her into relinquishing it. He then armed the Abronath and demonstrated its power on Syl.
Krall planned to use the Abronath to wipe out the millions of inhabitants on Starbase Yorktown, giving him a powerful base from which to launch further attacks against the Federation. Although his fleet of Swarm ships was destroyed by Kirk and his crew, Krall reached Yorktown's central atmospheric regulator, where the Abronath's effects would be disseminated throughout the station. Krall activated the Abronath, but was subsequently ejected into space by Kirk and consumed by the weapon. (Star Trek Beyond)
The Abronath consisted of a ring-shaped outer piece and a hexagonal center piece. It was armed by combining the pieces and submerging them in a metallic fluid. Once armed, the Abronath could be activated by turning the center piece clockwise, which caused it to release a cloud of particulates that rapidly disintegrated living beings on contact; if placed in a ventilated area, the cloud could spread to cover an enormous volume. The Abronath could be deactivated by turning the center piece counterclockwise, which caused the cloud to be drawn back inside the device. (Star Trek Beyond)