Frederick wandered aimlessly through the halls of Askr Castle. He'd recently been taken off the arena defense force, in favor of some strange mage known as "Ishtar". More like, Bitchtar he grumbled, before chiding himself on his language. The Great Knight felt disgraced, as he wasn't even considered an armored unit in this strange universe. Eventually, he came across an open room, that belonged to the Summoner. Everyone referred to the Summoner as "The Summoner", because everyone refused to refer to them as "LORDGRIMA_69". Frederick peeked his head inside, curious to what the room looked like, in case he was ever in a position to take care of The Summoner in a fashion akin to how he served Chrom.
Inside, there was some strange white artifact, with a logo on it. He pulled at the artifact, and it split in half, revealing a strange opaque surface, with runes on the other half. Frederick huffed quietly, tapping one or two of the runes, and was astonished when they pushed down, and the surface lit up. Well, he was just going to have to discover what this strange artifact had in store.
...
"Has anyone seen Frederick?" Chrom asked quietly.
"Can't say I have, Chrom." Xander replied, walking by with his apparently new "betrothed", some mage knight known as Reinhardt. Let it be known that everyone was inclusive, and that they were all proud of the Nohrian King being quite so... progressive.
"Blast. He's up for Arena Assault, with that new, even younger Sanaki, myself, and Camus." Chrom grumbled to himself. "Honestly, I don't think the summoner's so great at tactics. Their idea of strategy is to brute force everything..."
...
Chrom stumbled upon Frederick. "Frederick, there you are, come on, we have work to do!"
"Right away, milord." Frederick replied.
"Where even were you?" The exalt huffed as the two approached the debriefing room.
"Discovering these wonderful things called "memes", milord." The stoic man replied, not a hint of amusement in his face.
"I don't know what that is, but you need to stay away from that one mage that resembles my nephew. It seems he's rubbing off on you."
"Chrom, I'm certain that the mage you speak of is your nephew, only in a cheap disguise."
"Whatever. We're here."
...
It was their turn to go. Their motley crew of 4 faced off a team of all heavily armored beasts of enemies. Camus identified one of them as the Princess of Gra, Sanaki recognized a figure from her world known simply as "The Black Knight", and strangely enough, the remaining two figures were Chrom and Lissa clad in strange festive garb. The entire enemy team seemed to be favoring the Aether style of combat, and were all taking ferocious counterattack stances.
Frederick only grinned evilly, palming his Slaying Hammer. He then galloped directly ahead at the enemy team, gleefully calling out one of the new warcries he had learned from the artifact. "SKIDADDLE, SKIDOACHES, YOUR LAST BREATH APPROACHES!"
"I'm sorry, wh-" Sheena began before being slammed directly in the face by the hammer and launched completely off her feet midair into a tree.
"HIGH BST OVERRATED! DISCOUNT COUNTER OUTDATED! LONG HAVE WE WAITED! ATTACK MODE, ACTIVATED!" Frederick bellows mindlessly as he swats Lissa directly in the face with his hammer, breaking her nose with a bloody crack, and then having his horse kick the festive Chrom directly in the crotch.
Only the Black Knight was left. The two stared each other down. The Black Knight's insidious voice seeped from his helm. "You may be tough. But blades will always best axe-"
And the Black Knight was promptly cut off by Frederick leaning down from his horse and picking the Black Knight up by the top of his helmet. "Allow me to educate you. Axes are beat by Swords. Lances are beat by Axes. Swords are beat by Lances. The Weapon Triangle is beat by Frederick." With that, Frederick's hand squeezed, smashing the helm around the general's head, killing him instantly and removing him from the opposing player's account.
The rest of LORDGRIMA_69's party stared at him. "I will never surrender." was his only response.
(A/N: Frederick would most definitely ride into combat with a boombox playing music.)