Plague Bringer

Homebrew collection for plant, fungal, and decay stuff.

Some of the stuff on this link is repeated below.

Poligill's Circle of Decay

Symbiotic Partners [2]: You grow plants on your body. You get 1 type of plant at level 2, and another at levels 5, 10, and 15.

Empowered Partners [6]: You can use the Plant Growth spell to get a bonus effect from one of your plant partners, lasting 8 hours.

Empowered Host [10]: 1/Short rest: Cast 1 of 3 modified spells on yourself, lasting 10 minutes.

Reclamation of Nature [14]: Melee/Unarmed attacks vs beasts, humanoids, and undead deal 2d8 + Wis mod poison damage (DC 15 Con save for half).

Zardoz's Circle of Spores Overhaul

Halo of Spores: Removed.

Fungomancy: Adds 10 bonus spell known, gaining one at almost every level from 2 to 15.

Symbiotic Entity [2]: Renamed Fungal Bloom, bonus damage can be either Necrotic or Poison.

Fungal Slaves [6]: alters Animate Dead to raise plant zombies.

Necromantic Spores [10]: Fungal Bloom creates a 30' aura that heals your plant zombies.

Fungal Body [14]: Immunity to blinded,deafened, frightened, poisoned, and criticals.

Quoria's Circle of Spires Rework

Circle Spells: as UA.

Halo of Spores [2]: A Reaction triggered when you take damage. Releases a cloud of spores dealing poison damage to one creatures within 10'. Damage scales with level. Bonus: You treat Poison Immunity as Resistance for all spells and class features.

Symbiotic Entity [2]: 3 THP * Level. Halo of Spores damage doubles. 1/Turn, a melee weapon attack deals bonus poson damage to the target. Damage scales with level.

Fungal Infestation [6]: Creatures that die immediately after taking damage from Halo of Spores rise as zombies. HP = Druid level, Wisdom attack. Lasts 1 hour.

Spreading Spores [10]: Bonus action to hurl spores up t0 30' away, creating a 10' cube zone for 1 minute. Creatures that move through or start their turn in the zone take Halo of Spores damage. Zone disappears if you use this ability or Halo of Spores. Bonus: 1/Long Rest you can ignore Poison Resistance/Immunity to the damage of one spell or class feature.

Fungal Body [14]: Immunity to Disease and Poison (condition and damage?). 1/Long rest: If reduced to 0 hp you immediately activate Symbiotic Entity (regaining 1 use of the ability if none remain).

Beef Swellington's Circle of Pestilence

Not just another CoS rework.

Swarmshape [2]: You can wildshape into a Swarm of Insects (and variants). Add proficiency bonus to attacks made in swarmshape, and add 5 HP for each level beyond 2nd.

Caress of Decay [6]: Your melee attacks deal an additional 1d8 necrotic damage and deal 1 necrotic damage to everyone adjacent to you. At 11 and 17 add +1d8 to your attacks and +1 damage & +5' range to your AoE.

Corrupt Conditioning [6]: Resistance to Necrotic and Poison damage.

Feast of Filth [10]: Swarmshape can feed off corpses, healing 1d8+proficiency bonus every round.

Putrid Palate [10]: Immune to Poisoned condition from eating rotten food.

One with Disease [10]: Immunity to magical and non-magical diseases.

Contagious Aura [14]: Living creatures within 5' must make a Con save or become afflicted by a disease of your choice (as the Contagion spell). Saving = Immunity for 1 day. Max 1 disease/creature at a time. Can't turn this aura off.

Others:

Ivellius' Circle of Plagues

BradBrimstone's Circle of Pestilence