Since my drawing skill is absolute balls, the best I can do is give you guys a concept.
First, the basis. I should say that I hadn't exactly gone through all the channels to find this thing, since all I had to do was search "ghost plant" in wikipedia loooool. This is Monotropa uniflora, also known as the "ghost plant":
Here's a different angle:
The ghost plant lives in the dark and doesn't use chlorophyll (which would have worked quite nicely with the dark-sun abilities, but meh), but instead takes the energy from fungi who take THEIR energy from trees. So in a way, the ghost plant is "possessing" the fungus. A bit of a stretch, but it doesn't have to make complete sense.
This thing would also mesh well with the chosen abilities, since it shares a relationship with fungi, which produce spores (creating a protective "layer" or "shield" of dust-like spores), which is essentially what Shield Dust is. Also, its white colouring make it seem too "pure" to be effected by poisoning. You could also spin it the other way and say that its purity make it highly susceptible to poisoning, but since the other two Pokemon who have this ability are white in colouring for the most part, I think my reasoning is more justifiable.
Speaking of colouring, the ghost plant can also be found in a rare red colour, so we've got our shiny colouring ready made. Here:
Now for the application. First off, we could easily use the simple/unoriginal idea of slapping some eyes on it and making it into a serpent plant thing, but not only would that not comply with the ghost typing, it would also ignore the defensive direction we're taking with this Pokemon. The best options available to us would be to either change its form (similar to how Roselia is basically a woman with rose-like parts), or combine it with something else (i.e some kind of fungi). The latter works especially well, since the ghost plant has to "combine" with another life form in order to survive.
For example, we can use some of the ideas already suggested in the thread. We could merge it with the dead tree, since the ghost plant essentially lives off trees in real life anyway, simply using the fungi as an intermediate (although it is a DEAD tree...that could use some reworking lol). Or we could combine it with the giant blue thing CRASHiC posted, replacing the tentacle-like appendages on its body with the plant.
If we want to combine it with a fungus and keep with the zoology, we should use fungus of the family
Russulaceae, since that's what it lives off of. Otherwise, I'd say this plant can combine with just about anything. A white dog with 3 ghost plants for tails, a forest spirit with ghost plants for horns/antenna/extra appendages, etc.
![Terywj [태리]](/data/avatars/l/71/71007.jpg?1555906021){kind=avatar}
