This now has a canon answer.
This is Hive, also known as Alveus.
In the Marvel Cinematic Universe, Hive served the Kree, and was designed to command the Inhuman armies
However, his power grew too great, and he was banished to Malveth.
Hive is a parasitic life form that possesses various powers, including
the ability to infest and possess corpses, to take over Inhumans and
twist their personalities to serve him, to consume others in order to
make himself stronger, and to kill ordinary humans, either by
stripping the skin from their bones or by infesting them from the
As of Season 3 Episode 17, Hive inhabits the corpse of Grant Ward.
There is an interesting similarity between Hive and Kilgrave from Jessica Jones, both of whom possess the ability to force others to do their will through infection, though on the one hand Hive can only affect Inhumans, whereas on the other hand Kilgrave cannot change his victims' personalities.