[ Look, you know it has to be a different iteration of Gilgamesh if he's facing Saber in a maid outfit and managing to not even focus overmuch on that detail. Smh.

Actually, he even looks rather serious, having upgraded the discussion from idle thought to more serious consideration, especially with Saber's urgency. ]

There are two among the Outsiders who have. One is Ereshkigal, a goddess of my native pantheon. I do not know whether you might know her in her Servant form. The other is one Ratio, a doctor who is a scientist. Somewhat like that Romani, if that gives an idea.

[ Just totally blithely proceeding from the assumption that this Saber shares his summoning!! ]

I cannot say we know much more about the specifics... yet.