Rare Wondrous Item (Cloak), Requires Attunement

Gambit. At the start of combat, after rolling initiative, you may choose a single target that you can see and issue an unspoken telepathic challenge. They can either accept or refuse:

• Gambit Accepted. The target accepts the challenge and the following effects begin to affect you for 1 minute, until you are reduced to 0 Hit Points, or until you target a different creature than the target with an attack or a spell:
  • The target gains disadvantage on attack rolls against creatures other than you. 
  • When you issue the challenge, the target’s weapon attacks against you deal extra 2d8 force damage until the end of their next turn.
    • Once the target’s first turn since accepting the gambit ends, your weapon attacks against them deal extra 1d8 force damage for 1 minute, or until the effect ends. 
• Gambit Declined. The target refuses your challenge and the following effects begin to affect you for 1 minute or until you target a different creature than the target with an attack or a spell:
  • The target gains a +2 bonus to AC against your weapon attacks.
  • You score a critical hit on a 19-20 on your weapon attack rolls against the target (If you already have other ways to score critical hit on a 19 or even 18, the roll required to score a critical hit is simply reduced by 1 instead).
  • Once per turn, you can, when you roll for damage on a weapon attack against the target, you can reroll a single die and use either of the results. 

Duelist. Twice per Long Rest, you can use this item to cast Compelled Duel (DC 15) from it.