A stronghold located in the Danern Straits of Leasath, was an impregnable fortress and production facility of the Fenrir. It is housed on an island with a full view on all sides, preventing it from being invaded. It houses a Shock Cannon on the peak, similar to the Gleipnir's, although with a faster firing time.
Leasath-Aurelia War (Op. )
Archelon Fortress was assaulted and destroyed by Gryphus 1 and Aquila Squadron after it was revealed the Leasath Superaircraft Fenrir was being built there. The elite Alect Squadron intercepted them in the Fenrir, but fortunately a small Aurelian landing force was able to bypass the fortress's naval defenses and land on the island. They then proceeded to destroy the High Powered Microwave Emitter (HPM), nullifying Fenrir's cloaking. Along with it a Shock Cannon, seen on the Gelipnir, was installed onto the island, but was destroyed.
Gryphus 1 then destroyed all Leasath forces and proceeded to enter the fortress. The Aurelian ground forces planted explosives around the facility, causing it to self-destruct. Gryphus 1 managed to escape the base as it exploded in a massive fireball.
Sources
Ace Combat X: Skies of Deception (the game)