Rezo hesitates, both because he knows the pilot is listening and because he's honestly not sure where to start explaining.

"It's... what we would refer to as {astral shamanism} in my world. I am unsure how you would put it in Imperial. Outer space element magic, perhaps? Regardless, you needn't worry, as this spell is quite harmless."

For Donnie, and for the pilot for that matter, who is still alive and unhurt despite being unable to move.