The rocks that previously orbited it's former evolution now connect with Cragnorock's body; They form arms and basic hands to perform useful functions.
Similarly to the effect that evolutionary stones have on Pokemon, returning Asgraveil to it's crash site caused it to evolve into Cragnorock. Scientists believe this is due to the alien radiation left in the soil.
It collects all forms of minerals from the planet. It has been observed eating certain rocks and discarding others.