An affliction skirmisher works best when operating alone, they can work in teams but are a bad fit for conventional ones and are a bad choice to build a team around. They do best in misfit groups that focus on versatility. Due to their slow output of damage, at first, they need support from a good team that allows them to sneak in afflictions until those afflictions ramp up in damage. 

Afflictionist

Starting at 3rd level, whenever you hit a creature with a melee attack you can inflict an instance of Ruination of the Blood, Ruination of the Flesh, or Ruination of the Spirit.

• Ruination of the Blood: Inflicts an ongoing 1 necrotic damage until the affliction is cleansed. Additional instances have a cumulative effect.
• Ruination of the Flesh: Inflicts an ongoing 1 poison damage until the affliction is cleansed. Additional instances have a cumulative effect.
• Ruination of the Spirit: Inflicts an ongoing 1 radiant damage until the affliction is cleansed. Additional instances have a cumulative effect.

Your afflictions may be cleansed via any form of healing.

Shadow Stalker

Starting at 3rd level, you grow used to moving through the shadows and striking at your foes. You gain expertise in the stealth skill if you don't already have it, in addition you may use your bonus action to become completely invisible in dim or complete darkness for as long as you remain stationary.

Affliction Eater

At 9th level, you gain the ability to remove your afflictions from a creature, using it to heal yourself.

As an action, you may target a creature with a minimum of one affliction on it that is within 60 feet of you, you then remove the affliction, gaining a number of hitpoints equal to the number of afflictions removed.

You may use this ability a number of times equal to your proficiency bonus, you regain all uses at the end of a long rest.

Improved Afflictions

Starting at 13th level, whenever you hit a creature with a melee attack you can inflict an improved instance of Ruination of the Blood, Ruination of the Flesh, or Ruination of the Spirit.

• Ruination of the Blood: Inflicts an ongoing 1d4 necrotic damage until the affliction is cleansed. Additional instances have a cumulative effect.
• Ruination of the Flesh: Inflicts an ongoing 1d4 poison damage until the affliction is cleansed. Additional instances have a cumulative effect.
• Ruination of the Spirit: Inflicts an ongoing 1d4 radiant damage until the affliction is cleansed. Additional instances have a cumulative effect.

Additionally your afflictions may now only be cleansed via healing spells of the 6th level or higher.

Aura of Inevitability

Starting at the 17th level, your afflictions are so potent that they can self multiply within a creature's body. When a creature with your afflictions affecting it starts its turn within 15 feet of you, the afflictions on that creature double, while still being separate.

Ex. 2 Instances of Ruination of The Flesh and 3 Instances of Ruination of The Spirit = 4 Instances of Ruination of The Flesh and 6 Instances of Ruination of The Spirit 

In addition, your afflictions may only be cleansed by the Heal, Greater Restoration, or Wish spells.