I had to guess on that one because I had read all the books but never watched the later seasons of the show. It was still pretty easy to guess, though.
I'm such an idiot I read "Grendel" as "Gretel" like Hansel and Gretel and tried every variation of "the witch" I could, finally in deparation typing things like Hansel and "crazy woman in the woods" and random German names hoping that it was a reference to a specific movie I didn't know about. No actually I just can't read
My head turned Gredo into Fredo, spent too long trying to remember the name of the guy Michael sent to shoot his brother before I realised what the hint meant.
I don't know or care who Thanos is or was, but it would have been better for the world if he had just got on and killed all those people before we were given endless films and sequels about them.
As long as he was Abel!