Oath of Contagion.

Tenets of Contagion

Paladins who take the Oath of Contagion are reminded of their tenets by the rust on their armor or weapons.

Spread the Virus: whether it be to sicken your enemies or to cull the weak. all that come into contact with you must know about the virus you harbor so that they may spread its word, or literally spread it, as well

Grow the Plague: The virus inside you must feed on something, so why stop it, whenever the opportunity arises let the virus feed, whether it be you or your enemies, it must grow.

Offer No Cure: those that are sickened must either over come the sickness, or die to it, they must do this themselves without help, so you shall offer none, nor will you let other.

Oath of Contagion Spells

Paladin Level -> Spells

3rd -> Hex, Ray of Sickness

5th: -> Blindness/Deafness, Ray of Enfeeblement 

9th: -> Speak with Dead, Summon Undead.

13th: -> Blight, Vitriolic Sphere.

17th: -> Cloudkill, Contagion.

Channel Divinity

Contagious Presence: You can use your channel divinity to summon a great plague to infect your enemies. each creature of your choice that you can see within 30ft of you must make a Constitution saving throw. On a failed save, a creature becomes poisoned for one minute and takes 2d4 poison damage whenever they make an attack or cast a spell. The poisoned creature can attempt the saving throw again at the end of its turn, ending the effects on itself with successful save.

this damage increases to 4d4 damage at 11th level and 6d4 damage at 18th level.

Creatures with immunity to the poison damage or the poisoned condition make the save with advantage, and creatures with vulnerability to poison damage make the save at disadvantage.

Infectious Smite: When you hit a creature with your divine smite ability, or a smite spell, such as Wrathful Smite, you can use this ability, the damage type changes to poison, and the creature gains the poisoned condition for one minute, as well as the infected and contagious condition for 7 days. A creature may attempt to make a Constitution saving throw against your spell save DC at the end of their turn to end the poisoned condition. 

An creature with the contagious condition appearance to be sickly and gains the symptoms of the common cold, though they suffer no ill effects to any roll. Any creature that comes within 5ft of this creature becomes infected.

An Infected creature suffers no ill effects and appears to be fine even though they harbor your virus, though their thoughts might be slightly foggy. the virus can be detected by a Detect Poison and Disease spell. the creature can be cured by a remove curse spell or remove disease, or any spell that can remove disease or the poisoned condition. 

Sudden Plague

As an action you can bring lingering sickness to the surface of creatures you can see. choose a creature  with the poisoned condition that creature must make a constitution saving throw against your spell save DC, or target every creature of your choice that you can see with the infected condition on a failed save a creature takes 2D8 poison damage, and half as much on a successful save. If a creature has both the infected condition, and the contagious condition then that creature takes the poison damage an additional time. creatures with immunity to the poisoned condition or disease automatically succeed. This damage bypasses resistance to poison damage, and treats immunity to poison damage as resistance instead. (Creatures that started with immunity to poison damage that then went to resistance is then bypassed completely while in your Aura of Contagion range at level 7)

the damage increases to 3d8 poison damage at 11th level and 4d8 at 18th level.

Aura of Contagion

while you are not unconscious or incapacitated an aura of plague and sickness spreads around you in a 5ft radius but not through total cover. this sickness slowly makes your enemies slower and sickened, even if they are no longer threatened by sickness. While hostile creatures are within your aura of Contagion immunity to the poisoned condition and diseases and/or resistance to poison damage are ignored, and immunity to poison damage is treated as resistance. Additionally when a creature with the poisoned condition that usually has immunity to the poisoned condition leaves your aura of contagion that creature is still poisoned until the effect ends.

Additionally at the start of your turn choose one of the following to effect your enemies health.

• Slowing Sickness: hostile creatures that start their turn within your aura have their movement speed reduced by 5ft
• Sapping Illness: hostile creatures that start their turn within your aura make attack and damage rolls with a -1 to their rolls
• Weakening Ailment: hostile creatures that start their turn within your aura receive a -1 to Dexterity saving throws and AC

When you reach level 18 in this class your aura range increases to 30ft. and the effects increase to a -2 or to 10ft.

Never Ending Plague

When a poisoned creature within 30ft of you becomes no longer poisoned as a reaction you can attempt to bring new sickness to it, that creature must make a Constitution saving throw, on a failed save that creature is poisoned for one minute, and infected and contagious for 7 days.

Additionally you can use your bonus action to make all creatures within 30ft of you to have disadvantage on their next Saving throw against the poisoned condition. When you take this action creatures previously without resistance or immunity to poison damage are vulnerable to poison damage until the start of your next turn.

Lord of Contagion

Harrowing plague spreads through your body making you the harbinger of disease you gain the following benefits for the next minute.

• Melee weapon/spell attacks you make do an additional 4d4 poison damage.
• Hostile creatures within your Aura of contagion take 4d4 poison damage at the start of their turn, if a creature is poisoned that creature takes the damage an additional time.
• Your AC increases by 1 for every 2 creatures that have the poisoned condition from you
• Hostile creatures have disadvantage on saving throws to end the poisoned condition.
• When your HP is reduced to 0 you instead you gain +1 HP per creature that has been poisoned by you. This ends this ability and the poisoned condition on each creature.

Once you use this feature you may not use it again till you take a long rest.