It's basically the same thing as Cofagrigus, just possessing a bunch of rocks instead of a sarcophagus. Hell, it even comes from Yamask.
Sorry op for hijacking - but that’s where you’re wrong my dear reoccurring reblogger, and read this with just as much joy as I’m delivering it,
Cofagrigus is a human soul taking the form of a coffin! The same way yamask holds its mask so dear because it’s the face of its past life, Cofagrigus has just as much love for its resting place! That coffin is its phantasmal flesh. And that’s where the Unova lore ends - and really, the lore for Yamask and Cofagrigus as well.
Runerigus is a cursed deity of the art it represents (presumabley.)
So even in the form of a yamask, we’re no longer looking at a true human’s soul anymore. It’s been replaced.
Here’s the Game Data for Galarian Yamask!
We don’t know what Runerigus is.
It possessed a Yamask, and requires this ritual to “evolve” into its true form.
That’s right, trainers! Put this entity’s yamask vessel through enough pain in the right spot, and the terrifying dark curse of an art god will reassemble itself!
It fed off of Yamask’s (a human soul’s) mourning and grief. Now it’s at its full power, no longer even categorized as a Cofagrigus.
This isn’t just an evolutionary chain. It’s a tragedy!


















