Notes:

the onix screeched, bellowing and tumbling through the tunnels, this strange creature latched to its face, merging with it, forcing its essence into the onix's body.
And it caused the poor frightened rock snake to tumble and burrow toward the one substance that would cause its demise.

Water.

HURR, i saw this fusion and the first thing i though was
OH GOD PARASITIC FACEHUGGER SENTIENT EVIL STARFISHHHHHH