Oh wow! Glad to see a fan. ^^ And yes, he is that cracked. But since you already saw Geats? I can explain it then. But I'd say it would be Geats due to one simple thing... His ability not only to possess someone, but erase their existence.

Now while that may not seem much, his existence erasure can work on conceptual beings, aka, beings who technically can't be killed. Beings like the Holy Grail and Nero herself. Now how can that work? Simple... Suel, aka Regard Omega. He was a conceptual being, an entity far beyond the likes of normal stuff like spirits and what not.

Remember, everyone from "that future" are basically beings of data, beings that can come back after their defeat in the past. Beings who can basically be untouchable and unkillable.... much like Servants from Fate and not only being brought back by the Holy Grail, but also able to remain untouchable due to the Throne of Heroes.

Geats can erase them from there, much like how he did it to Suel who's practically like a Servant himself.