He was imprisoned in Nibelungen for a thousand years, only to find out upon his release that he was

[Type-Moon]
On the first day of the journey, a rainy night, on an overpass, the one-eyed deity, using time-stop, attacks.
It's Odin from the Dragon Clan. A terrible start, he's doomed!
On the second day, what? Odin, you failed to kill me with your elbow? You used the Nibelungs to trap me instead?
Then I'll have to come and elbow you every day!
Decades later, a bunch of people fell in one after another.
White-haired, red-eyed Ishtar? I don't recognize her.
I didn't travel through Fate, so it's normal.
Francesca boasted about her illusions. What's so special about that? It's just a dream-inducing technique.
I taught her a few Odin dragon runes, and she started yelling about primordial runes.
The mysterious woman in black robes is a fanatic who calls herself an Assassin.
Without a skull mask, the disguise is off. His assassination skills are nowhere near mine.
His alchemy skills improved so much that he reached the level of the "Seven Kingdoms".
Hmm? What do they mean by saying I've entered the realm of magic?
……
After more than a thousand years, they finally broke free.
Wait, the Holy Grail War is underway? So I'm in Type-Moon?
Wait, what do you mean I became the End Device, the Grand Dragon, the Lostbelt King, and the Primal One (UO)?
(Odin from Type-Moon can actually stop time; setting from fle)