I think it´s the floor´s master last effort, remember the "sea slug"it digievolve at some point in its fight
Well we know the bosses do form changes at some point, but with the Minerva hypothesis that the floors of this dungeon are on another continent, that its boundaries have enchantment magic applied, the weird voice he hears that seems to be from the dungeon, and the big monkey being fairly intelligent, I'm just wondering if this form change, which is may be something provided by the dungeon is also a result of magic and that the big monkey is self-aware and applying the dungeon-provided enchantment himself to do the form change?
I figure this boss will eventually be beaten and that they'll move to the next floor, and I'm curious if we'll start seeing other humanoids, or even humans, as bosses, who would just straight up use magic.