|Out of universe information|
Osiris' Jaffa was an unnamed Jaffa in the service of Osiris. He was seen at the Pel'tak of Osiris' Ha'tak and seemed very loyal. He informed Osiris that Anubis had arrived and stood loyally to Anubis when Anubis arrived on the bridge. He was some time later ordered by Osiris to have the coolant of the engines be vented into the lower decks which stuns Colonel Jack O'Neill and Teal'c. He was still on the Ha'tak when Osiris and a landing party of Jaffa arrived at the surface of the planet they were orbiting. He was on board when Osiris' Ha'tak was forced to flee after that it is unknown what happened to him but it can be assumed he is still alive. (SG1: "Revelations")
He appears to serve under Osiris on his Ha'tak, but the mark on his forehead is actually Anubis's mark, not Osiris's, meaning it is truly unknown if he is a jaffa of Anubis or Osiris.