You have the ability to craft specialized Witcher potions and blade oils with the use of their Alchemist’s supplies, which you gain proficiency with. A Witcher must possess all required materials and succeed on an Intelligence DC equal to 10+ the difficulty of the potion or oil they are trying to create. Each potion has a toxicity value associated with it. A Witcher can only consume a number of Witcher potions per day equal to their Constitution modifier plus one half their current Witcher level (minimum 1). If a their toxicity level exceeds their limit, each hour they must succeed a Constitution save until they are able to complete a long rest (DC equal to 10+their current level of toxicity). On a failed save a Witcher takes 1d6 acid damage for each point they are above their limit.  If a Witcher’s toxicity reaches more than double their limit they must make a Constitution saving throw or be immediately reduced to 0 hit points. The DC for this save is equal to 12 + their current level of toxicity. The various potions and blade oils that a Witcher can produce are listed below:

• Thunderbolt: You gains advantage on attack rolls for 1 round per Witcher level. Difficulty: 2 Toxicity: 2 Components: 2 Witcher Potion Materials, 1 Rare Witcher Potion Material.

• Cat: You gain Dark vision up to 120 feet in complete darkness (in shades of gray), and can see up to 60 feet as though it were bright as day, for a number of hours equal to your Witcher level. Difficulty 1 Toxicity: 1 Components: 1 Common Witcher Potion Material

• Blizzard: Your reflexes are greatly improved and they gain a +2 bonus when making Dexterity saves to avoid taking damage. This effect lasts for 1 minute per Witcher level. Difficulty: 2 Toxicity 2 Components: 3 Common Witcher Potion Material

• Black Blood: Your blood becomes corrosive and acidic, damaging creatures that would drink it. Whenever a creature successfully makes a bite attack against you, they take 1d4 acid damage, multiplied by you Constitution modifier. This effect lasts for up to 1 minute. Difficulty: 3 Toxicity: 3 Components: 1 Rare Witcher Potion Material, 1 Common Witcher Portion Material  

• Petri’s Philter:  Creatures you target with your signs have disadvantage on any saves rolls made to avoid damage or status effects. This effect lasts for up to 1 minute. Difficulty: 2 Toxicity 1 Components: 2 Common Witcher Potion Material 

• Swallow: At the beginning of each round you regain HP equal to your Constitution modifier. This effect lasts for up to 1 minute. Difficulty: 1 Toxicity: 1 Components: 2 Common Witcher Potion Materials

• White Honey: You are cleared of all potion effects and their current toxicity level is halved (rounded up). Difficulty: 1 Toxicity: 0 Components: 3 Common Witcher Potion Material

• Killer Whale: You are able to hold your breath for an additional number of minutes equal to your Constitution modifier before having to hold your breath normally. Additionally you gain low-light vision underwater up to an additional 30 feet beyond your dark vision. Difficulty: 3 Toxicity: 2 Components: 1 Rare Witcher Potion Material, 2 Common Witcher Potion Material 

• White Raffard's Decoction: You regain an amount of HP by rolling your Hit Dice a number of times equal to their Constitution modifier. Difficulty: 4 Toxicity: 4 Components: 2 Rare Witcher Potion Material, 2 Common Witcher Potion Material

• Werewolf Decoction: You gain an additional 60 feet of Darkvision allowing you to see as if in bright light and are immune to Bludgeoning, Piercing, and Slashing damage from Nonmagical Attacks that aren't Silvered. These bonuses last for a number of rounds equal to your Constitution modifier. Difficulty: 5 Toxicity: 3 Components: 2 Rare Witcher Potion Material, Lycanthrope Fur.

• Troll Decoction: Your Strength score increases by 2 and you regenerate 5 hit points at the start of each of your turns. If you take acid or fire damage, you do not regenerate hit points at the start of your next turn. While under this effect you are only knocked unconscious if you start your turn with 0 hit points and do not regenerate. This effect lasts for a number of rounds equal to your Constitution Modifier. Difficulty: 5 Toxicity: 4 Components: 3 Rare Witcher Potion Materials, Troll Tongue

• Earth Elemental Decoction: Your Constitution score increases by 2 and you gain a +2 natural armor bonus to your AC. This effect lasts for a number of rounds equal to your Constitution modifier, before adding the bonus to your Constitution from this effect. Difficulty: 3 Toxicity: 3 Components: 2 Rare Witcher Potion Material, Earth Elemental Essence

• Basilisk decoction: You are immune to any and all Petrifying Gaze- like abilities. This effect lasts a number of rounds equal to your Constitution modifier. Difficulty: 3 Toxicity: 3 Components: 2 Rare Witcher Potion Material, Basilisk Fang

• Necrophage Oil: The Witcher’s blade is coated in a special oil that  is especially damaging to certain types of undead. When attacking with a weapon that has this coating on it you deal an additional 1d4 points of damage equal to half your current Witcher level, rounded down (minimum of 1), against creatures with the Undead sub-type (this damage does not apply to: vampires, wraiths, specters, shadows, banshees, and ghosts). A weapon with this coating is treated as magical, for the purpose of bypassing damage resistance. Difficulty: 2 Components: 2 Common Witcher Potion Materials

• Insectoid Oil: The Witchers blade is coated in a slimy, almost acidic, substance that is extremely harmful to Insect-like creatures. When attacking with a weapon that has this coating on it you deal an additional 1d4 points of damage equal to half your current Witcher level, rounded down (minimum of 1), against creatures with the Insect sub-type. A weapon with this coating is treated as magical, for the purpose of bypassing damage resistance. Difficulty: 3 Components: 2 Common Witcher Potion Material

• Vampire Oil: The Witchers blade is covered in a material that causes a severe allergic reaction Vampiric creatures and their spawn. When attacking with a weapon that has this coating on it you deal an additional 1d4 points of damage equal to half your current Witcher level, rounded down (minimum of 1), against creatures with the Vampire sub-type. A weapon with this coating is treated as magical, for the purpose of bypassing damage resistance. Difficulty: 4 Components: 2 Rare Witcher Potion Material

• Beast Oil: A blend of herbs, fluids, and secretions of various creatures, creates a mixture that is harmful to almost any mythical beast or monster that one can imagine. When attacking with a weapon that has this coating on it you deal an additional 1d4 points of damage equal to half your current Witcher level, rounded down (minimum of 1), against creatures with the Monstrosity sub-type. A weapon with this coating is treated as magical, for the purpose of bypassing damage resistance. Difficulty: 4 Components: 3 Rare Witcher Potion Materials

• Elementa Oil: Through a careful combination of natural materials, the Witcher is able to create a special oil that is able to make creatures from the Elemental Planes vulnerable to their weapons. When attacking with a weapon that has this coating on it you deal an additional 1d4 points of damage equal to half your current Witcher level, rounded down (minimum of 1), against creatures with the Elemental sub-type. A weapon with this coating is treated as magical, for the purpose of bypassing damage resistance. Difficulty: 4 Components: 3 Rare Witcher Potion Materials

• Ogroid Oil: Goblin, Orcs, Bugbears, Ogres, and even some Giants, often share a common thread of ancestry or have a shared bloodline. Because of this Witchers are able to concoct special oils that are particularly effective against these creatures. When attacking with a weapon that has this coating on it you deal an additional 1d4 points of damage equal to half your current Witcher level, rounded down (minimum of 1), against creatures with the Giant, or Humanoid (orc, goblinoid, grimlock) sub-types. A weapon with this coating is treated as magical, for the purpose of bypassing damage resistance. Difficulty: 3 Components: 2 Common Witcher Potion Material

• Specter Oil: By collecting the residue left behind after vanquishing incorporeal spirits, Witchers are able to create a specialized coating that is able to seemingly cut through the Ethereal Plane and strike these creatures as if they were solid. When attacking with a weapon that has this coating on it you deal an additional 1d4 points of damage equal to half your current Witcher level, rounded down (minimum of 1), against Specters, Wraiths, Shadows, Banshees, and Ghosts. A weapon with this coating is treated as magical, for the purpose of bypassing damage resistance. Difficulty: 4 Components: 2 Rare Witcher Potion Material, 1 Common Witcher Potion Material

• Draconid Oil: While as a general rule Witcher do not hunt Dragon, or there kin, that does not mean they are unable to do so. Only through obtaining very rare materials from magical creatures in addition to Dragonsblood itself can a Witcher create a potent enough oil to allow them to actually pierce a Dragons hide. When attacking with a weapon that has this coating on it you deal an additional 1d4 points of damage equal to half your current Witcher level, rounded down (minimum of 1), against creatures with the Dragon sub-type. A weapon with this coating is treated as magical, for the purpose of bypassing damage resistance. Difficulty: 5 Components: 3 Rare Witcher Potion Material, Dragonsblood

You may consume a Witcher potion at the same time you could consume any other potion. Applying a Witcher blade oil uses a players action and provokes an attack of opportunity. You may only brew potions and decoctions, or prepare blade oils, when during a short or long rest.