I just got two skeleton traps spawned in one thunderstorm on my Hardcore world... the second batch spawned right after I killed their riders... (one of the horses, unfortunately, died tho) :
Skeleton trap trapped itself, probably the easiest skeleton horse I have ever obtained. : r/Minecraft
What is a Skeleton trap in Minecraft?
How rare is it to find the skeleton trap horse? When I saw the skeleton horse get struck by lightning I was freaking out. : r/Minecraft
How to Summon a Skeleton Trap (4 Horsemen) in Minecraft