[quote=@MangoJuice]
<Snipped quote by orangebox>

Then we have the problem of who would be playing them, a GM or whoever discovers the old territory first? How would they know how they would behave, etc.
[/quote]

I suppose it can be played out like it was a wild animal for the Yelbs with their character sheet as a reference - sort of like an 'animal-pedia'? But since there isn't a character sheet for the Katyushas...