WARNING: The following material has not yet had a chance to become canonical.
Warning: Unmarked spoilers ahead.
Vasharesh is a late, impromptu addition to the pantheon. He has a perfect command of the mind - both his own and, more importantly, those of others, being able to read and rewrite memories and personalities of his victims. The kavkema consider him a deeply terrifying demigod, so fundamentally disturbing that adherents of various religions attribute his appearance to a ripple through the universe that allowed some of Garukaron to fragment, come loose and become autonomous. Religious opinions have yet to settle, though. Given his 'psychic ability', some also consider him part mammal, and thus under (perhaps involuntary) command of Tkanetar.
As he's not a stable concept in any one mythology, there's no means to attribute him primarily to any particular faith - but it's clear that he corresponds to the fallen Threadwielder Valcen, who in a desperate bargain is working for the Nayabaru as to leverage their technology (vastly superior to that of the kavkema) to realise his own plans.