He is known by many names, including that of “Shuustak” by the more savage and primitive creatures like Lizardfolk and Troglodytes.
The most common sub sect or cult of Sunstealer is Tenebraeth. Some say it is a child of his, other an avatar, some a fiend or spirit bound to the god. It is even said that this is just a made up name, so that those seeking to gain power from it do not have to use his name among the Dark Trinity. Regardless of its specific manifestation, it is synonymous with the god. He is the stealer of dreams, and despoiler of rest. Tenebraeth replaces dreams with nightmare, and traps those that he/it curses in a mind-prison of their own thoughts. There is no way to summon Tenebraeth in the light – the light of truth destroys the dark thoughts that surround Tenebraeth.