The Agrat-mot Nebula was an interstellar gas cloud located in the territory of the B'omar Sovereignty, in the Delta Quadrant.
The nebula was a key resource in the B'omar's trade negotiations with the Nassordin in 2374. As a result, the B'omar rejected a proposed route by USS Voyager through their space because it passed too closely to this nebula. (VOY: "The Raven")
This nebula was only mentioned in dialogue.
The Agrat-mot Nebula was named by Bryan Fuller. He took inspiration for inventing the name from a book about angels which he owned. (Information from Larry Nemecek)
According to Star Trek: Star Charts (p. 88), the USS Raven was lost in 2354 in the star system FGC-7861340. This system was located in or near the nebula.