You channel the rotting divinity of the Horseman of Pestilence, becoming a living plague-bringer.
Upon gaining this feat, you choose one of two modes.
You may switch modes during a short or long rest, or immediately when you are reduced to half HP or lower (your choice).

Both modes share the following passive base effects:

✦ Pestilent Flesh

You gain:

• Resistance to necrotic damage

• Advantage on saving throws against being poisoned, diseased, or paralyzed

• Immunity to nonmagical disease

✦ Aura of Rot (Passive)

A 10-ft aura surrounding you.
Creatures that start their turn in the aura take:

• 1d6 necrotic damage

• Must succeed on a Con save (DC = 8 + prof + Con) or are Poisoned until the start of your next turn

You can deactivate/reactivate this aura as a bonus action.

MODE 1 — BLIGHTED TITAN

The mode of endurance, spread, and battlefield control.

You become a hulking mass of plague-swollen, rot-resistant flesh.

Blighted Vitality

You gain temporary hit points equal to your level at the start of each of your turns.
(These do not stack — they refresh.)

Rotten Fortitude

When you take damage, you can use your reaction to reduce it by your Constitution modifier + your proficiency bonus.

Miasmic Bulk

Your Aura of Rot becomes 15 ft.

Hostile creatures treat squares in the aura as difficult terrain.

Fumes of Stillness (1/Short Rest)

As an action, you exhale a rot-fog cloud:

• 15-ft radius

• Lasts 1 minute

• Creatures inside the fog have disadvantage on attack rolls

• When a creature enters or starts its turn inside, it must succeed a Con save or have speed halved for 1 minute

You are unaffected by the fog.

MODE 2 — VIRULENT REAPER

The mode of aggressive infection, damage-over-time, and life denial.

You become a skeletal, fever-eyed avatar dripping with plague ichor.

Rot Reaper

Your melee attacks deal extra necrotic damage equal to your proficiency bonus.

Infectious Strikes

When you hit a creature with an attack:

• It must make a Con save

• On a failure, it contracts Virulent Sickness, taking 1d6 necrotic damage at the start of each of its turns

• The effect lasts 1 minute

• Additional failures add another 1d6 to the ongoing damage (up to 3d6)

Devouring Plague

Whenever a creature affected by your Virulent Sickness takes damage from it:

• You regain HP equal to half the necrotic damage dealt
  (Minimum 1)

Apocalyptic Sporeburst (1/Short Rest)

As an action, unleash a burst of spores:

• 20-ft radius

• Con save

• 4d8 necrotic on fail, half on success

• Creatures that fail also become Poisoned for 1 minute

• You may choose any number of creatures in the radius to spare

Plague Ascendant (1/Long Rest)

When you are reduced to 0 hit points, you instead drop to 1 HP and undergo a plague-wrought transformation for 1 minute.

During this state:

Your Aura of Rot expands to 30 ft, deals 2d6 necrotic, and inflicts Poisoned automatically.

You gain temporary hit points equal to twice your level.

You radiate an aura of life denial:

Healing from spells or abilities in your aura is halved.

You immediately activate the active ability of your mode without expending its daily use:

• Blighted Titan → Fumes of Stillness

• Virulent Reaper → Sporeburst

This transformation ends early if you are incapacitated.