Battle of Ulixis
Waged as part of the Crusade of Iron, the battle began when a combined fleet of Legio Lysanda and Legio Oberon vessels intercepted a distress call from the world of Ulixis in Ultramar. The loyalists decided to respond despite misgivings from Legio Oberon Princeps Tetaros Kast, wishing to trap the Legio Infernus on the ground by blockading their fleet and gaining access to Ulixis' munitions. After arriving at Ulixis, the loyalist vessels drove the traitor Titan transports and escorts from orbit and made planetfall A half dozen maniples of supporting Knights accompanied the Legio Lysanda and Legio Oberon, aiding the loyal Imperial Army and turning the tide of the raging war on Ulixis. At the city of Ulantia-Primus in Ulixis' great southern continent, the loyalist Titans battled their arriving traitor counterparts amid the winding avenues and artificial plasteel canyons. At the fore of the loyalist forces was Raynal Hess and his Warlord Titan Astra obsurus.
After wading through the burning streets and annihilating traitor Imperial Army, Hess' Titans crashed into the farmlands surrounding Ulantia-Primus. Expecting to find enemy Titans waiting, they instead encountered empty ruined landscapes. It soon became apparent that the enemy had been swept from the battlefield save for scattered traitor Army units. Horgoth Nyr and the Legio Infernus then sprang their trap against the loyalists, moving their fleet out of hiding and attacking the loyalist vessels in an ambush. The loyalist vessels were forced to flee, leaving the Legions on Ulixis to their own fate. Revealing they had originally sent the distress signal in the first place, the Fire Masters struck at Ulixis with the greater measure of their Legion. After a fierce orbital bombardment which saw many of the loyalist engines take shelter in the caverns of Ulixis, Nyr landed his own Titans. The traitors reclaimed the territory they had previously lost, bolstered by Dark Mechanicum forces. They chased the loyalist Titans into Ulixis' caverns, engaging in vicious subterranean battles for several days. The loyalists under Kast and Hess resorted to hit-and-run tactics, the largest of engagement of which took place at the Plasma Reactor vault known as the Wyrms' Lair. In the pitch darkness the two sides clashed, and Hess charged to meet Nyr and his Warlord Titan Mons Ingnum. However Nyr had laid yet another trap, and Hess and the Astra Obsurus were brought down by his hidden support Titans. In desperation, Hess detonated his Titan's reactors and set the entire Wyrm's Lair alight. In the aftermath a gigantic hole had been blown into Ulixis, and to the surprise of surviving loyalists their fleet had returned with reinforcements. Though Nyr and many of his followers had managed to escape, the loyalists had driven back the Fire Masters.