(covers information from several alternate timelines)
Altamid was an M-class planet located in the Necro Cloud nebula. It was once inhabited by an advanced, space-faring civilization, later called the Ancient Ones. Altamid was characterized by massive subterranean development with little-to-no life forms detectable from orbit. However, it had forests and other plant life.
In 2164, the Federation starship USS Franklin crash-landed on Altamid. Only three crew members survived, including Captain Balthazar Edison and his officers Anderson Le and Jessica Wolff. Unable to contact Starfleet and seeing no sign of rescue, Edison and his crew came to embrace an anti-Federation ideology.
Discovering a cache of technology left behind by the planet's former inhabitants – including advanced mining technology, a drone workforce, thousands of ships and a device capable of extending life by draining energy from victims – the three survivors resolved to make humanity strong again through war. They began to use the technology on the planet to raid unsuspecting ships and drain their crews, becoming Krall, Manas, and Kalara in the process and seeking out the Abronath, a lost weapon native to Altamid. (Star Trek Beyond)
In 2263, Krall learned that the missing half of the Abronath had been discovered by the USS Enterprise and was currently being transported aboard that ship. He instructed Kalara to pose as an alien whose ship had crashed on Altamid, luring the Enterprise to the planet's system, where it was attacked and destroyed by Krall's swarm.
While the remains of the Enterprise crashed onto the surface of Altamid, many of the survivors were captured by Krall and imprisoned in his compound. Most of the Enterprise senior staff managed to elude capture and soon rescued their shipmates using the transporter aboard the long hidden USS Franklin. The Enterprise crew eventually escaped the planet aboard the hastily repaired Franklin, pursuing Krall to prevent him from releasing the Abronath on Starbase Yorktown and the Federation at large. (Star Trek Beyond)
Altamid featured a diverse topology ranging from craggy canyons to lush forests. Extremely tall trees marked the landscape in one location. Another location was distinguished by golden yellow rocks, another – the area later held by Krall – by blue quarries.
Star Trek Beyond co-writer Doug Jung once noted of Altamid, "We had loftier ambitions about that planet from early on." According to Jung, Altamid was intended to be "essentially a mining colony," rather than a home planet. 
On 26 July 2016, Pegg News – a Twitter account moderated on behalf of Simon Pegg – provided a brief description of Abronath which mentioned Altamid, describing it as "an M-class planet in the southern spiral arm of the Andromeda Galaxy." According to the tweet, Altamid was the only planet where the metal known as Abronath could be found. The tweet concluded, "Altamid has endured several mass extinctions due to the presence of Abronath in its asthenospheric crust."