So, the players that I DM for have been amassing allies for a final large battle. One of these allies is an Oath of Conquest Paladin that has transformed into a Death Knight since they last saw him. Upon learning that the Paladin is unavailable to help they might try to scry on him to find out what's going on (they have been scrying a lot lately).
From the Monster Manual Death Knights entry:
When a paladin that falls from grace dies without seeking atonement, dark powers can transform the once-mortal knight into a hateful undead creature. A death knight is a skeletal warrior clad in fearsome plate armor. Beneath its helmet, one can see the knight's skull with malevolent pinpoints of light burning in its eye sockets.
The Scrying spell states:
You can see and hear a particular creature you choose that is on the same plane of existence as you.
The computer I am currently on has sage advice blocked, but I remember seeing something about the spell showing the caster the corpse of the creature if it has died.
If the caster chooses the Paladin, does the Scrying spell work and show them the Death Knight?