Phyrexian Sleeper Agent

Tailored to compleating select areas or individuals from within, sleeper agents can be dispersed months or even years prior to Phyrexia invading their targeted area. They are made to secure positions of power or influence, and then burst from hiding with phyresis ready to spread. Almost all sleeper agents are unaware of their hidden nature, and further unaware of Phyrexia's existence. Because of this, phyrexian sleeper agents can be of any rogue subclass, but immediately become this subclass if their phyrexian nature is revealed for any reason, losing their prior abilities and gaining these ones. Using this subclass implies that your role as a sleeper agent has already become activated. 

Oil Coat

Starting at 3rd level, you can use the bonus action granted by your Cunning Action to coat your weapon with glistening oil. The next time you hit a creature before the end of your next turn, if they were not infected with Phyresis already, that creature must make a Phyresis infection saving throw.

Infectious Touch

When you choose this archetype at 3rd level, you can infect certain surfaces by coating them in glistening oil. As an action, you can coat a surface up to a total of 10 square feet in a thin layer of glistening oil. This oil cannot be created in a space a creature occupies, and at least part of the area has to be within a range of touch.  Any creature who touches this oil for the next hour must make a Phyresis Infection save, either becoming infected or advancing their infection stage on a failure. A creature cannot be effected by this ability more than once every 24 hours, and if you use this ability again, any previous areas effected disappear. 

Unnatural Reflexes

Starting at 9th level, once per long rest when you would fail a dexterity saving throw, you can use a reaction to succeed instead as your phyrexian augmentations pull you out of danger. 

Corrupting Kill

By 13th level, you have enough oil to ensure those who fall stay fallen. Once per dawn , whenever you kill a non-phyrexian creature, that creature's body becomes infused with phyrexian oil. If the creature is restored to life prior to the oil being rendered inert, that creature is restored to life as a phyrexian version of it's previous race. This process also allows for the creature to be restored to life without requiring the material components of the spell that did so. 

Redeployable

When you reach 17th level, you have become adept at returning to what you once were. If no living creatures are aware of your phyrexian nature, as part of a long rest you can retake your mantle as a sleeper agent or enter a new one. Any of the glistening oil on your person can be disguised as magical acids, and you do not look like a phyrexian. However if you are revealed again or use one of your subclass abilities, both of these properties deactivate once more.