Scisers are clawed amphibious predators found on Zebes. Some were brought to the Biologic Space Laboratories research station's Sector 1 and Sector 4, where they were later infected and mimicked by X Parasites. Scisers seem to be crustaceous in appearance. When found on their home planet, Zebes, they can be seen following a set, continuous path. The X-infected versions, however, move in repetitive, left-to-right patterns and can shoot energy balls from their claws. A Sciser-X's physiology is also quite different from its uninfected form. They can be found crawling around on the floor, walls, or ceiling.
In certain areas of the BSL station, uninfected Scisers can be seen in the background, and free-floating X Parasites will usually proceed to infect these; in rare cases, they will spontaneously form a Gold Sciser-X. These are much stronger than their average counterparts, and their claws can block some of Samus' weaponry.
There are withered, rotten corpses of Scisers in Draygon's chamber. They may have been used as sustenance for the Evirs and Draygon.
This species shares some similarities with the Tallon Crab, as they are both crustaceans which possess three eyes.
While uninfected Scisers from both Super Metroid and Metroid Fusion possess three eyes, the X-mimics and infected variants found in the latter game have two eyes only. The loss of their middle eye is attributed to the X's gene manipulation.
The fact that Sciser-X can shoot energy balls from its claws may or may not have been a reference to Crabmeat, a crablike enemy from the Sonic the Hedgehog series. If that were the case, then whether or not it was intentional is unknown.
The creatures name may derive from the word Scissor, which is a cutting tool usually paired in two that looks similar to this creature's claws.
Scisers are one of the few enemies easily dispatched with the Grappling Beam; this can help make short work of them in earlier encounters.