Plague brush

A plague brush was a monstrous planar plant creature that was quite simply an enormous tumbleweed. In the Great Wheel cosmology, they rolled across the scarlet plains of Cathrys, second layer of the Tarterian Depths of Carceri, while in the World Tree cosmology they were swept across the Barrens of Doom and Despair, but it was not unknown for them to somehow cross into other planes.

Description
They were massive balls of vines that grew to the size of a building, most being some and the most massive weighing up to. However, its volume was mostly empty space, with relatively little plant matter in the form of vines making up the rest.

Behavior
The single instinct of the plague brush was to roll over things, crush them, and kill them. However, it wasn't very accurate, nor thorough—it might roll over some unfortunate, then forget them entirely. A plague brush was as likely to roll through a camp or settlement and continue on its way as it was to barrel through and destroy all in its path.

Combat
A plague brush attacked by rolling into something or over something, and it did both with devastating force. Worse, those it rolled over risked being caught in the vines, scooped up, and taken away with it. Any creature smaller than the gigantic plague brush could be caught inside, to be steadily crushed and presumably consumed.

As it was mostly empty space and it was always rolling over, it was exceedingly difficulty to attack a plague brush effectively. Any piercing weapon or projectile, like a spear or arrow had a chance of missing, simply going right through the plague brush without damaging it.

Abilities
The plague brush was constantly enveloped by a cloud of spores, to a radius of. If inhaled, they caused a virulent wasting disease called "greensickness" that drastically deteriorated one's strength and their health.

Background
Strangely, artwork of the plague brush appears in the online art gallery for Fiend Folio 3rd edition, but the creature does not appear in the actual book, suggesting it was removed prior to publication.