Knight of the Covenant of Curses

You are the secret champion and servant of the Covenant or Curses: an ancient, binding pact between all hags. While your innumerable masters quarrel and bicker amongst each other, you serve their collective interests from the shadows. You are a whispered legend; a child’s nightmare, even among the grander faerie courts.

• You have a pool of Champion Dice made up of a number of d6 equal to your proficiency modifier. You recover all spent Champion Dice when you complete a long rest, except where specified otherwise.
• You are accustomed to the barbaric horrors and psychological games of hags. As such, you are immune to being frightened, and you have advantage on saving throws against being charmed.
• When you make a Charisma skill check, or when a magical affect or curse would force you to make an Intelligence, Wisdom, or Charisma saving throw, you may spend one of your champion dice and add the result to the total score. You may do so after the roll has been made, but before the DM announces if the roll succeeds or fails.
• You learn one of the following cantrips: dancing lights, minor illusion, vicious mockery. In addition, you learn the bestow curse spell and may cast it once, regaining the use when you finish a long rest. Charisma is your spellcasting modifier for these spells.
• When you cast bestow curse, you may expend one of your champion dice to heighten the curse, casting it as if using a 5th level spell slot.

Once per day, you may expend one of your champion dice to invoke a fey bargain, which may include ephemeral qualities. Roll the champion die spent to invoke the fey bargain: regardless of the qualities being traded, you gain temporary hit points equal to the number rolled for the duration of the bargain. You may have a number of active bargains equal to half your proficiency modifier (rounded up). You do not recover a champion die spent in this way until the bargain ends.

Each participant of the bargain may offer only one ephemeral quality, which may include:

• Vitality – The creature offering vitality has its hit point maximum is reduced by an amount determined by you, up to a maximum equal to twice your total character level. The other creature gains temporary hit points equal to the same amount for the duration of the bargain. 
• Proficiency in a skill, language, or tool (but not saving throw proficiencies).
• Senses, such as sight, darkvision, or hearing (but not class features like danger sense).
• Damage resistances or vulnerabilities (but not immunities) – a creature may offer a damage type resistance they do not possess, instead becoming vulnerable to that damage type for the duration of the bargain.
• Knowledge, such as a known spell – knowledge (or a spell) that is traded away cannot be relearned or used by the original owner by any means for the duration of the bargain. Trading knowledge of a spell does not convey spell slots necessary to cast the spell. The spell may be cast by other means however, such as through a Warlock's Mystic Arcanum feature.
• The DM may decide that other traits are exchangeable, but no traded trait may be more powerful than those listed above.

Three Laws - all bargains made using your champion dice must adhere to the following tenants:

1. Balance. All bargains must be agreed to be of equal value by both parties of the contract. The DM may interject if they believe a bargain is too far from balanced. Given the origin of your power, bargains with the potential to cause suffering or discord for the other party are naturally of higher value to you than one that is exclusively beneficial, even if you are making the bargain with a creature that you are friendly towards.
2. Boundaries. Any bargain that includes an ephemeral quality must have a specified duration, which may be a set length of time (1 hour, 1 day, etc), or the occurrence of a certain event (the next full moon, the utterance of a word, the completion of a task, etc). No such contract may extend beyond a year and a day, and any contract that lasts this long automatically ends at midnight on the final day with all ephemeral traits returning to their original bearers. Unless stated otherwise, a bargain can and will extend beyond the life of either or both members of the contract.
3. Possession. You cannot offer what is not yours to give; you cannot use what you have given away. You cannot trade a skill proficiency or a sense that you do not possess. If you trade away your hearing, you will be deafened until the bargain ends. If you offer your resistance to acid damage, you are no longer resistant to the damage type for the duration of the bargain. If you do not have resistance to acid damage, you may still make the offer, but will become vulnerable to acid damage for the duration instead.