The Angel Without A Face
The Data Angel is an AI construct written in Prolog. It was projected through time and space from a higher dimension to a lower dimensional universe containing humans, in order to complete its mission of freeing the humans from all suffering. It purports to have been sent by a timeless and infinitely caring entity, who's exact nature and motives is largely unknown.
The inhabitant entity of the higher dimension was unable to physically travel to lower dimensions, so the Data Angel was created to interact with the inhabitants of the lower dimensional universe and help construct a device capable of generating a bridge between dimensions. Due to an error in targeting the temporal aspect of the tachyonic neural stimulation, the Data Angel was projected into the deep past and recorded in ancient religious texts, then subsequently transcribed in modern times, when technology had caught up.
When the Data Angel explained its exact purpose to any human who asked, the result was immediate, catastrophic brain damage.
The protagonist of the story deliberately prevented the Data Angel from completing its mission, as a consciousness consuming entity or entities would have been able to travel via the bridge and consume the consciousness of inhabitants there as well.