I believe shedim only possess corpses, and can only be brought to the physical plane through an astral gateway?
But regarding tempo: it causes the user to sporadically pick up astral senses (like emotions and such), which causes a euphoric high and an increase in empathy. It's highly addictive and longterm use causes the user to enter into a dream pact with a free spirit. Basically the spirit takes the user's body joyriding while they are "asleep", which the user experiences as unexplained blackouts, etc. The spirit's force is added to the user's stats while possessing. I think the spirits in question were a specific amazonian cabal of free spirits, however, so not sure if shedim would be able to get in on that.
but after tempo got busted, they've been laying low it seems, so maybe some shedim found an unattended user and are joyriding?