I was sort of thinking of Simas as a "skin spy - Wathi doll" but it does make sense that it had to be some sort of accidental rare occurrence.
If the Inchies could either make ensouled skin spies, or count on it occurring randomly at any appreciable rate, it would be game over for the humans of Earwa.
It only makes sense that this single or exceedingly rare freak occurrence would be embedded at the Mandate, rather than being used to chuck fireballs at nomadic northern tribes.
But, does anyone have a proposal on how such a freak cosmic occurrence could take place?