They used a Ketch to nuke Rezyl, then the Kell came down from the Ketch to show off or take his corpse as a prize. They had assumed he and his Ghost were both dead because that’s normally enough to kill a Guardian and their Ghost together, but Rezyl had left his Ghost away from the battle so it could come and revive him after he lured out the Kell. Taking the full corpse as a trophy is odd, but Fallen have a habit of taking Ghost Shells or other things as trophies. Riksis took skulls as trophies and Taniks supposedly took many body parts as trophies.

....you telling me Ketch’s can nuke?!?!.....I want one......