Egarus (Void Mould) - A Horrible Thing from Planescape

Planescape is beloved for good reason. It introduced another amazing setting (actually building on the foundations laid before in products such as AD&D's Manual of the Planes) and introduced an amazing cast of new monsters, universes, magics and allies. 

It also introduced some truly deadly hazards, many of which were, in truth, too vicious to use in many settings. One of these was the Egarus fungus...

Egarus is, to put it simply, a fungus that cannot tolerate anything other than nothingness. Planescape cannon suggests it started as an Abyssal fungus that was carried into the Plane of Vacuum, that adapted to survive in that utterly inhospitable environment, and learned to sustain itself on nothingness, actually seeing any kind of "something" as a threat. Thus was the Egarus - an organism that just wants to return any non-void environment into a vacuum state - born.

I have no idea where (or even if) I would use this, but here is my 5e take on this horrible, horrible organism...and even a little bit about where it may possibly lurk in my game universe. 

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It's here already!!!!
EGARUS FUNGUS (Void Mould): Grows in clusters of 1d3 patches, each one occupying a roughly 5ft area. Whenever anything other than vacuum comes within 25ft of it, it begins to attack, affecting things in the following order, one per round, acting on Initiative count 20. If there are multiple possible targets in range, it attacks one at random, though always in the order outlined below;

1st: Energy: one source of light or energy, or one active spell, or magical / psionic effect within range ends.

2nd: Life: One living thing within the area must make a D.C. 18 Constitution saving throw or begin to suffer 55 (5d10) bane force damage at the start of each of their turns. Once they have begun to take damage, the target must receive either a Greater Restoration or a Wish spell, or the damage continues until they are destroyed. They are slain and destroyed when they reach 0 hit points, and can only be returned to life through the use of a Wish or similar.

3rd: Materials: Five cubic foot of material within range is disintegrated. Magical items may attempt a D.C. 18 Saving throw against Force damage to avoid this. When the Egarus disintegrates the ground on which they lie, they fall and continue to grow on the new surface.

Each time a single target (regardless of what it is) is consumed by the fungus, it spreads to an adjacent area, in effect, forming another 5ft patch of Egarus.

Disintegrate, finger of death, greater restoration, lightning bolt, power word kill, shocking grasp spells destroy a patch instantly, as does the application of any acid, alcohol, lightning attack, or even a large amount of water (at least 60 gallons). Hold monster or slow stop the egarus from attacking. The fungus is immune to cold, fire, physical attacks, and most spells other than those discussed above.

When anyone attacks the Egarus, it forces them to make a D.C. 18 Wisdom saving throw, failure indicating that they suffer 55 (10d10) bane force damage as teleports random areas of their body away.

Egarus are usually only encountered in void dimensions, such as the Plane of Vacuum or certain planes of imprisonment. However, there are unsubstantiated claims that Egarus may have been “accidentally” sealed in with the contents of several of the hidden Guild Vaults, and that when they are opened and returned to the physical plane, they will be full of nothing but boiling, black Egarus – and oblivion). Clearly, the opening of such infected vaults would be catastrophe capable of ending the world if it occurred.