The eyeball plant is a type of plant found only in The Maw of Chaos. Eyeball plants grow in groups, and although they do not attack or do anything threatening, they will watch intently anything moving that enters their field of vision. The visual acuity of the plants is very high; they can spot Garrett at distance in deep shadow.
The plants will die, leaving no trace other than a pool of blood (with a satisfying squelching sound) when hit with the sword enough times.
The eyeball theme may be an allusion to the incident in TDP/TG involving The Eye and Garrett's eye, although its earliest model, the Periscope Plant does not support this.