I also was rather confused as to what it was all about, so I spent all my money (350k) on one.. Basically you right click it, and it turns you into the monster it says. The maker, some kind of European character, apparently sucks the soul out of a monster and can turn it into a mask. Now I assume it has to be a monster that can be killed by the maker, so naturally I'd assume a mask for a Niya General would be worth a hell of a lot more than a mask that can turn you into a Mangyang.
Keep in mind it only lasts 30 minutes (from memory) and you can't teleport. I crossed a ferry to show myself cruising around as a white tiger, and when I teleported it went away

Also you can't use any skills whil wearing the mask, and I assume you
can PVP wearing a cape and probably
can wear a job ID either. It's really just a novelty, serving no real tactical purpose, but it does make the game a little more fun.
Yes you can summon a wolf, so I was a tiger, cruising around with a wolf, which was kind of cool. But you can't use skills of any kind, so your attack will be identical to that of the monster whose soul your have adopted.
I think it's be cool to be a yeoha or something with a ranged fireball-type attack, but that's just me.
I've seen prices vary between 200k - 800k, but eventually I suspect the level or 'coolness' of the monster will dictate the price it's sold for.
Have fun
