Plague Doctor

A New Kind of Doctor

You have studied long the inner workings of blood of beast and man. After gaining extensive knowledge of how these creatures work you think you might be able to exploit this knowledge for better or worse. Plague Doctors use their Intelligence to guide their hand as Medic and Rogue alike. Knowing just where to poke to get the desired results. 

Medical Practitioner

Your study in Medicine has allowed you to use your Intelligence to better your skill. Starting at 3rd level you gain the following benefits;

• You gain proficiency in Medicine if you do not already have it.
• You gain Roguish Expertise in Medicine when you take this subclass.
• You can use Intelligence in place of Wisdom for Medicine skill checks.

Eye for Arteries

With understanding of most creatures' insides, you learn how to make them outsides. When you take this subclass at level 3 you can observe a creature for any specific weak points. As a Bonus Action make a Medicine skill check on a creature within 60 ft that you can see. The DC is 8 + the creature's CR. On a success, you may Concentrate for up to 1 minute. During this time you may add Sneak Attack and your Intelligence Modifier to the damage of your first attack against the creature each turn, even if you do not have advantage, but not if you have disadvantage. This effect ends if you are incapacitated, lose concentration, or use this ability again.

Medicinal Concoctions

You carry with you a set of chemicals and materials to produce various spell-like properties. Your practices might seem like magic to some but your results are indisputable. When you reach 3rd level, you gain the ability to prepare a list of spell-like Concoctions. You choose these from the Plague Doctor Spell List.

Power of Science. Because of the nature of your practice, you are unaffected by Anti-Magic fields and similar spell negating, or spell casting restrictions..

Spell Slots. The Plague Doctor Spellcasting Table shows how many slots you have to cast your Plague Doctor Spells. To cast one of these Spells you must expend a number of Spell Slots equal to the Spell's Level. You regain all spell slots when you finish a long rest.

Spells Known of 1st-Level and Higher. You know two 1st-Level spells of your choice from the Plague Doctor Spell List. The Spells Known column of the Plague Doctor Spellcasting Table shows when you learn more Plague Doctor spells of 1st level or higher. Each of these spells must be of a level for which you can cast, as shown on the Plague Doctor Spellcasting Table.
Whenever you gain a level in this class, you can replace one of the Plague Doctor spells you know with another spell of your choice from the Plague Doctor spell list. The new spell must be of a level for which you can cast.

Spellcasting Ability. Intelligence is your spellcasting ability for your Plague Doctor spells, since you learn your spells through dedicated study and memorization. You use your Intelligence whenever a spell refers to your spellcasting ability. In addition, you use your Intelligence modifier when setting the saving throw DC for a Plague Doctor spell you cast and when making an attack roll with one.

Spell save DC = 8 + your proficiency bonus + your Intelligence modifier
Spell attack modifier = your proficiency bonus + your Intelligence modifier

Author Note.
Many Plague Doctor Spells come with various titles that indicate the general usage of the spell. Unless the spell specifies otherwise the likely usage of the spell is as follows;

• Poultice. A dry powder or pasty substance that is usually applied directly to the intended target. Poultices often need specific mixtures to react but can have violent reactions such as the Burning Poultice.
• Oil. Used to coat or cover something. Oils can include Venomous poisons, Oils of Invisibility, or something as simple as a Dye.
• Elixir. Intended for consumption. Elixirs' main purpose tends to be a kind of potion-like liquid. Elixirs can be ingested poisons, healing remedies, personality and body altering substances, or even wild and violent effects.

Eye for Injuries

Beginning at level 9 you gain the following;

By using one of the Bonus Actions granted by your Cunning Action you can make a Medicine skill check on a creature you can see within 60 ft. The DC is equal to 20 minus half the creature's missing Hit Points. On a success you know the creature's Hit Point maximum, and current Hit Points. After succeeding on a check against a creature you can accurately tell its current Hit Points for the next 24 hours without needing additional skill checks or actions.

You may spend 1 additional minute observing the creature to determine any disease, injury, or otherwise unseen ailment. Make an additional Medicine skill check on the same creature after observing it. Gain advantage on the skill check if the creature is willing and within 5ft. The DC depends on the type of ailment(s), decided by the DM. If multiple ailments plague the creature make the skill check with disadvantage, even if the creature is willing. On a success you know exactly what condition(s) ail the creature and how to cure them, or how to obtain knowledge on curing them.

After observing a creature for at least 1 minute you automatically gain knowledge of the creature's maximum and current Hit Points for the next 24 hours.

Eye for Vulnerabilities

At 13th level you can accurately tell any damage vulnerabilities or resistances that a creature you can see within 60 ft might naturally have. This ability cannot determine resistances or vulnerabilities granted by spells or magic items. Additionally, you can accurately determine the unarmored AC of a creature within the same range.

Mortician

Beginning at 17th level, any time you succeed on a Medicine check on a creature you gain knowledge of how to kill that creature. This includes any resistances, vulnerabilities, natural AC, and maximum and current Hit Points. Once you gain knowledge on a creature in this way you never forget this information about that creature or similar creatures.

Any time you land a critical strike against a creature you have knowledge of, all base damage die are treated as maximum rolls. Only roll the critical strike's additional damage die.

Once you gain knowledge of a creature you gain knowledge of how to create a poison or venom capable of killing it. You may create the poison during a long rest. The ingredients for the poison cost 500 gp x the creature's CR. Alternatively the DM may allow you to gain knowledge of how to obtain ingredients necessary to poison the creature. You can only create enough poison for a single dose or coating on a weapon or piece of ammunition. Any amount of the poison is lethal to the intended target, all other creatures take poison damage equal to 1d4 x the intended creature's CR. The poison retains its potency for 24 hours after being applied to a weapon, or after being successfully applied to a creature.