I was always kind of operating under the assumption that Hecate was secretly one of the demon generals (considering the necromancy), but I wonder if this general calling her "Lady Hecate" (-sama) means she's someone more important, like the demon princess or something. Or heck, maybe even the demon "king" herself. The way he says "give up on humanity" here kinda makes me think Hecate is less going against the demon king, and more attempting to use the hero (and humanity by extension) as some kind of experiment/test.