A Cyst is an immobile Necromorph that usually grows on or near the Corruption, preventing anyone from moving through its immediate vicinity.
Cysts are basically land mines that do not have a mind of their own. They throw organic bombs out of themselves when ever something approaches it, regardless of what it is. They can be used as an enemy or ally depending on its position. They can kill Necromorphs or you depending on if you're aware of their position and what you do with them. They can be easily identified by the noises they make, which sounds like ragged, heavy breathing.
- A Cyst bomb/mine can be picked up/caught with Kinesis and used as an explosive weapon to kill the Cyst or other Necromorphs.
- Catching a Cyst's mine and then throwing it back and killing the same Cyst will earn you the Bouncing Betty achievement in DS2.