CW: This article contains graphic imagery.
The cvorvatian brainworm is an incredibly dangerous, life-sucking and life-giving, worm native to the planet Cvorvatis. This worm species is rather peculiar; it seeks out any lifeform nearby, either consuming its brain matter if there is any or substituting it and taking over the host's body through a series of neural networks.
These brainworms are naturally found in icy terrains amongst the mountains and Poles of Cvorvatis. Due to increased space traffic in the urban regions of these areas, the worms have found themselves on other planets, clambering aboard spacecrafts. They are well suited to environments with or without atmospheres, so long as they can consume brain matter at least once every Cvorvatian month.
Brain matter is the only thing these worms can consume. Unusually, they cannot detect the food itself, but rather lifeforms in general. Once a lifeform is located they will attempt to bury into it, digging around the body whilst secreting a numbing agent so they go undetected. Once the brain matter is located the worm will consume every last atom of it, before morphing into a gelatinous liquid that will harden to form an egg of a new brainworm.
What's less horrific is when the worms locate a plant, fungi, or rather, anything without a traditional brain. The worms will find the warmest spot within this organism and will serve as its brain instead, secreting liquidid neural networks that can transmit signals from every single part of the body to the worm. For stationary organisms the worms will also generate primitive skeletal structures and muscle tissue which allow them to locomote. Reports of plants and fungi uprooting themselves and slowly walking around forest floors come from all across Cvorvatis, as well as several neighbouring planets.