((Oh, hey, I recognize these things. Never actually played Warhammer 40k, but I like the fiction/lore and I've played the video game.))
Whether his companion manages an exit or not, Ordo will rush the nearest Flayed One, raising his bonespear and attempting to impale it.
If he succeeds, he'll lift it above his head and toss it away against the nearest hard surface.
Even if Necrodermis is far too thick for bonespears and superstrength, the sheer blunt force of the natural weapon's impact should do something.