You are dying.  This infection will claim your life at some point and you have accepted the inevitability of it, though there may be a way to become one with it.

Terminal Illness

You are deeply afflicted with an infection, for reasons unknown, you are unable to be cured.  You know that it will eventually take your life.  You stare death in the face everyday, and every morning you wake still to find yourself still among the living is a surprise.

This resignation to the inevitable has made you immune to charm and fear.

When you are in a grapple with a target they must save versus Constitution or be infected.  While diseased they receive only half of any healing effects.

Passing the Vail

At level 6 choose one of the two following options, this selection will also dictate your level 14 option.

Vegepygmy

You are deeply afflicted with Russet Mold.  When you die your corpse will sprout forth a Vegepygmy, you might even pass away in your sleep during a long rest.  The Vegepygmy that sprouts forth, for reasons that are unclear, inherits your persona.  When this happens then you lose any abilities that are specific to your race such as darkvision, water breathing, or flight.  You are also no longer Infectious, but do retain any feats and your immunity to Charm and Fear.

• You gain resistance to lightning and piercing damage.
• You have darkvision to 60 feet.
• Lastly, your size is now small.
• You are considered a Plant for purposes of detection and targeting.

Wood Woad

You willingly offer up yourself to be sacrificed and become a Wood Woad.  You lose any abilities that are specific to your race such as darkvision, water breathing, or flight.  You are also no longer Infectious, but do retain any feats and your immunity to Charm and Fear.

• You gain resistance to bludgeoning and piercing, and vulnerability to fire.
• You gain darkvision to 60 feet, and climbing speed of 30 feet.
• Your size is medium regardless of what it used to be.
• You are considered a Plant for purposes of detection and targeting.
• You are no longer infectious.

Acceptance

At level 14 you gain an option dictated by your selection at level 6.

Mold Begets Mold

You grow tougher and have developed spore clusters on your body.  You are deferred to by other Vegepygmies, so outsiders refer to you as a chief.

You can expel spores in a burst, infecting nearby creatures.  If a creature dies while infected, its corpse produces Vegepygmies or a Thorny the same way russet mold does.  You can release Spores once per day as a 15 foot cloud that extends around corners.  Each creature in that area that isn’t a plant must succeed on a Constitution saving throw versus your Constitution modifier or be poisoned.  While poisoned in this way, a target takes 2d8 poison damage at the start of each of its turns.  A target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

You are Infectious again, if you are grappled by or if you grapple a creature then it must make a CON save or be diseased with russet mold.

Symbiosis

Once on each of your turns, you can use 10 feet of movement to step magically into one living tree within 5 feet of you and emerge from a second living tree within 60 feet of the first that you can see, appearing in an unoccupied space within 5 feet of the second tree. Both trees must be Large or bigger.

You gain the Shillelagh cantrip, which you can use on a club that you produce from your own body at will.

Fl-or-a Fauna?

At level 18 you gain the following abilities:

• You have Plant Camouflage, which give you advantage on Stealth when obscured by plants.
• You are able to Multiattack, you can perform two attacks as your attack action.
• When you take damage, as a reaction regain one hit die (1d8 + CON) hit points at the start of your turn.  If you take cold, fire, or necrotic damage, this trait doesn’t function at the start of your next turn. You die only if you start you turn with 0 hit points and don’t regenerate.