Serris (イシュタル Ishtar) is the third boss Samus Aran faces aboard the Biologic Space Laboratories research station in Metroid Fusion. Serris' habitat is located in Sector 4 (AQA). Serris is a long, aquatic, serpent-like creature. Adam describes it as a "very large creature" that is "capable of moving and attacking at ultra-high speed". Considerable damage was done to Sector 4 before Samus arrives; while the damage that was done to the sector that was seemingly coordinated and deliberate was likely committed by the SA-X, the more wide-spread and senseless damage is believed to have been done by Serris. There is a breeding tank in the sector which Serris often returns to; Samus must reach it in order to terminate Serris, despite it being a "valuable specimen".