A rancid, writhing mass of grime, puss, disease, rot, and scum. This is The Filth, the embodiment of all things unclean in existence. Warlocks that work to spread The Filth are awarded with its foul powers. Embrace disease. Embrace rot. Embrace The Filth, and you will be greatly rewarded.

The Filth Spells

The magic of your patron ensures you always have certain spells ready; when you reach a Warlock level specified in the Filth Spells table, you thereafter always have the listed spells prepared.

Filth Spells

Warlock Level	Spells
3	Grease, Tasha's Caustic Brew, Melf's Acid Arrow, Wither and Bloom, Acid Splash
5	Gaseous Form, Stinking Cloud
7	Blight, Vitriolic Sphere
9	Cloudkill, Contagion

Septic Mark

When you swear fealty to The Filth, your disgusting patron has infused your magic with its own putrid, rotten essence. Starting at 3rd level, when you hit a creature with an attack roll, you can call upon your patron to rot your target from the inside.

The target is marked as Septic for 1 minute or until you lose your concentration (as if you were concentrating on a spell). The first time on each of your turns that you hit the Septic enemy and deal damage to it, including when you mark it, you deal an additional 1d6 acid damage to it.

You may also choose to forgo the additional damage and instead force the creature to make a Constitution save against your spell casting DC. On a failure, the creature has disadvantage on attack rolls and ability checks until the start of your next turn. You may mark a creature this way a number of times equal to your Proficiency bonus per long rest.

Rain of Filth

Starting at 6th level, as a vessel for The Filth, septic and corrosive sludge oozes and splatters from your pores with every move you make. As a bonus action, you may have a creature you can see within 60 feet of you make a Constitution saving throw against your spell casting DC or take 1d6 acid damage and deal that same damage to all other creatures and structures within 10 feet of them. Septic creatures instead take and deal 2d6 acid damage.

Wave of Nausea

Starting at 10th level, you practically drip with sludge and grime, leaving a trail of pollution in your wake. You can now produce a concentrated cloud of putrid stench.

Once per short rest, as an action, you may summon a cloud of fetid ichor in a point you can see up to 100 feet away. The cloud lasts for 1 minute, takes up a 20 foot radius sphere, and spreads around corners and over obstacles. The foul odor of the cloud is so intense that it leaves its victims doubled over in painful nausea.

Whenever a creature enters this horrid area for the first time, or starts their turn there, they must make a Constitution save against your spell casting DC or take 2d6 necrotic damage and be rendered incapacitated until they leave the area of the odor. A creature that makes this save takes half the damage and may continue unaffected. Septic creatures make this save with disadvantage. 

Fetid Residue

Starting at 14th level, you have become the emissary of The Filth. You are a walking infection, a vile husk of pure grime and ichor. Your magic is sickness given form, and its wretched influence stains all it touches.

Whenever a creature you can see within 60 feet of you dies, you may use your reaction to cause the creature's body to burst with a wet pop. Oozing puss and septic gore splatters all creatures within a 15 foot radius of the corpse.

Creatures in the area must make a Dexterity saving throw, taking 3d8 necrotic damage on a failure and half on a success. Creatures that failed the save also take 1d8 acid damage at the start of each of their turns for 1d10 turns as the toxic entrails cling to their bodies. Septic creatures make their save with disadvantage.