Where are the Dark Menhirs during the Grandmaster Battle?

 Here they are!

No they don't move, and they self disappear after 30 seconds.

Also, if they 1hko, then all the warriors would have died during that. They definitely don't 1hko, though they do form some sort of a blockade when you corner Margana. She's really slow though (and even slower after I slowed her) so she stayed pinned.