I love doing realistic versions of Pokemon, plus I'm trying to practice at digital stuff more, so here ya go.

I based Yamask off the Egyptian Ba bird, and chose the African pygmy falcon as visual reference. Yamask is well known for being once human, and for possessing anyone who tries to wear the mask. My theory is that Yamask is the Ba, eternally searching for it's counterpart, the Ka, which it's supposed to meet up with in the afterlife, though obviously that didn't happen. Now, one's Ba is their core, it's their personality, it's everything that made them who they are, so of course Yamask would retain the memories of it's former life. The Ka is what distinguishes a living person from a dead person, so it stands to reason that Yamask would be attracted to it, though seeing as how the Ka it finds is still attached to a living body, Yamask would be unable to continue on, and would instead be trapped inside the physical shell holding the Ka, and would overshadow the Ba of the original body.

And of course when it evolves it eats living human beings and turns them into mummies, which would release their Ka. Unfortunately, it also would release their Ba, and so the Cofagrigus would still be unable to carry on into the afterlife. It sucks being a Ghost-type!

Image (c) Scott Francis
Yamask (c) Nintendo