Run by GA America, Arteria Ulna is one of the first Arteria seen in the game. It is located within a deep and lengthy canyon that is somewhat narrow, making it easy to defend and protect. It is composed of several buildings that are built directly on the canyon walls and floor, with the Arteria energy transmitters located on a ridge, protected by Normals. There also appear to be several propellers mounted on the canyon walls, which are inferred to be wind turbines. It appears in the mission "Destroy Arteria Ulna."
- Although taking this mission does technically put the player on the ORCA path, the player still has the option of completing League assignments, putting them back on the League path.