For Ackster, drinking the blood leaking from the hole in the centipede's layer of armor was more symbolic than about physically consuming the blood since it just flowed straight through his bare skeleton. Fortunately, that was all Ackster needed for Monster Muncher to take effect and begin extracting the essence, existential power, nutrients, mana, and life force from the centipede's blood.
Of course, the amount Ackster could get from even a couple of mouthfuls of blood was minimal since the centipede was so ridiculously large. But the blood gave Ackster the energy and enough recovery to resist death long enough to crawl inside the centipede.
The higher temperature threatened to break apart and turn his skeleton to dust. That was why Ackster chomped down on the rough meat as soon as his head was inside.
