I had a crazy theory about the seemingly "undead" creatures of the Ancient city. I was thinking, since the Skull warriors look similar to Toa, what if the Protectors lied, and the Toa are simply one of many teams summoned to try and deal with the threats within. The previously summoned teams all perished and were reanimated, and these Toa are the first to finally succeed. Thus, the Skull Grinder/Slicer ect. are all previously summoned Toa who were killed and raised by Makuta (Or whoever is behind all this.)