Military action
Wanting a port on Horizon's eastern coast but finding a decent locale difficult because of all those pesky mountains in the way, Antecea opted to take the dwarven city of Kal Undrumm (which would later become Precipice) instead.
The city was heavily fortified thanks to its advantageous position of inside a goddamn mountain, but not to be deterred, Antecean spies sabotaged the city's legendary Obsidian Forge, causing an explosion that ripped apart the mountain, exposing the interior to the sea, and allowing the Antecean Navy to swarm the city virtually unopposed.