From above, Nathaniel watched Surtur's legions and his own rallied forces clash in earnest. It was a murky blur beneath him with only a pop of orange mystical energy to prove to the God of Darkness that one of his friends was still within the battle. Besides Thor of course, whose heavy artillery status was in no danger of being rebuked.
Momentarily confident that the battle was well in hand, Nate yanked hard on Major's reins and forced the pegasus higher. The God of Darkness and his steed rocketed toward the center of the mighty black stone fortress and with a finally tender stroke of Major's mane, Nathaniel fell from the saddle. He struck the wall with reckless abandoned, but instead of being smashed against the rocks, he entered the darkness and vanished from the sky. Nate's body, his essence traveled through the castle and reappeared inside of the gothic throne room. From the sunken position, Caltrops heard Major's shriek, the beast had circled the spires before returning to the sorcerers for the battle.
Nathaniel eyed his goal, Surtur, and the massive demon of fire and destruction stood from his cobbled-together throne. Body and sword already aflame, he seemed unimpressed.
"Do not waste my time. Bring me Thor. Only one raised by Odin could be so disobedient toward the laws of nature," Surtur instructed what must have been the Allfather's herald. "Asgard will fall and death will come even for the mighty sons of Odin. I was created to bring that destruction and no army can change that fact."
Nate smiled while his mask remained cold and even-tempered. "You are correct, Surtur," he started and he released his sickles to the ether. Neither dropped, but instead, shadowy tendrils snatched the handles and they floated beside him. "Death and destruction will come for Asgard and eventually win. Darkness will one day claim this entire universe," Nate admitted then clasped his free hands behind his back. "But my fiery friend, you played your role, and this realm isn't your second chance," he informed the undead force of nature and then his weapons advanced.
"Petulant child!" Surtur's graveled exclamation hurled toward Nathaniel while his arms swung his sword.
Nathaniel's blades descended on the skeleton's form and buzzed around the giant, wasps on a hostile intruder. Metal struck bone and piece by piece Surtur collapsed, his over-sized blade falling mere inches from Nate's position. The final pass separated the demon's head from his neck and the fire within the bones was exhausted. Nathaniel pulled off his mask and carefully approached the decapitated being. He pulled his glove and brought his palm down on one of the demon's horns. He closed his fist around the sharpened edge until blood trickled out. Nate pulled his hand away and slammed it onto Surtur's forehead. "I offer this sacrifice to oblivion itself," he whispered then heard the swirling whine of the void. Surtur's throne shook and collapsed, the pieces absorbed by the black-hole opened beneath it. Nathaniel pulled the head of his enemy up the dusty stairs and dropped Surtur's skull into the maw of darkness. "I claim this castle, this realm, and the mantle of death!" Nathaniel exclaimed, then stared into the darkness. Hypnotized, Nathaniel fell forward and disappeared from the throne room.
The next time he witnessed light again, it was within that same throne room. The torches of Loki's freed warriors were the glow, each of them knelt around Nathaniel. "How long..." he asked, then realized it must not have been very long... the sounds of the battle outside still raged on. "Right," Nathaniel reached to pull the mask down over his face but discovered a crown atop his head. He paused and fought to remember anything within the void... but there wasn't time. "Outside!" he yelled and pointed toward the heavy doors which now opened on his command. "Your comrades flirt with nihility on your behalf!" he called, and they yelled, then they ran for the battle proper.