Hatura decided to create a strain of genetically modified Ishim for spying, surveying, assassination and similar purposes. Thanks to their exclusive access to details of the Ish genome, they were able to form legions of such new beings.
Sodim differ from default Ishim in many aspects. Notably, they are inherently submissive to most peoples thanks to their lower placement in the Scale of Being as novel homunculi. Sodim have rounder wings which lack oil altogether. This means their flight is silent, like an owl's. They usually tuck their arms to also reduce drag and noise in flight.
The eyes are jet black, adapted for night vision. Their halo is also non-glowing, simply golden, being naturally covered by a thin light-filtering pellicle. And their feet are feathered, similar to a ptarmigan's, but with owl-like feathers which mute steps.
Another trait designed for sneaky missions is their venom. In each forearm, a Sod has a gland which produces anaesthesia and an amnesiac fluid. This venom can be pumped through their fingers and claws.
From the Hebrew סוֹד (sod), "secret".