The Reaper does not show up on Custom Dungeon's normal floors
Apparently once I got the reaper event and after struggling to find the spring he never showed up. So to test it I grabbed the custom dungeon test sample that was given during the open beta or somewhere there I can't remember and tried to get the reaper event using a mod that shows the reaper timer aka how much time you have left until the reaper shows up and it doesn't show anything nor he appeared