Feralighoul by @Eternity9

I see Feralighoul just 100% being a costume monster instead of an actual creature, though maybe the in-universe costume designers based the design on some rumours/myths about an unusual Feraligatr?. If it was a ‘Real’ Pokemon (It would have visible eyes for starters) it would be a rare Water/Ghost type Feraligatr that’s only seen in one particular swamp, it would be either an endangered variant being the last of its kind or a ‘One-off’, the origins of are unknown, but it’s basically a Boss/Totem/Noble Pokemon of it’s area protected by its Warden/Locals who want to protect their rare Pokemon.

Edit: I forgot to add the design is based on the Gator Ghoul from the Scooby Doo episode 'The Gruesome Game of the Gator Ghoul'