The Alakagross Civilization, also known as the Alakagross Precursors, were
an idea borrowed from Umbra's fic Poke-Dwemer a society of Abra and Beldum line members who formed civilizations predating humanity's, beating them (and other mons) to the punch by virtue of their sheer intelligence. However, the civilization was destroyed by the Legendaries when a civil war led one side to attempt to activate the Mt. Pyre Caldera. Chrome is one of the few survivors.
The Alakagross were keepers of highly advanced technology, including the airships used during the Draconic Uprising and the golem Numidium, all made using Deep Alloy. Most if not all Alakagross technology seems to have an incredible resistance to wear and tear, with automatons such as their Centurions working as if they were brand new despite having being hundreds of thousands of years old.
Glitchstuck Wars reveals that they were capable of interstellar travel, but for the most part appeared to stick to their home planet.