Hard Eight

2nd-level enchantment (luck)
Casting Time: 1 bonus action
Range: 30 feet
Components: V, S
Duration: Concentration, up to 1 minute

You stack the odds for a willing creature you can see. At the start of each of your turns while concentrating, roll on the Gambit (d8) to set this round’s rule for the chosen creature.

Base effect — Doubles pay: When the creature hits with a weapon attack that was rolled with advantage or disadvantage, if any two d20s rolled for that attack show the same number (doubles), the hit deals an extra 1d8 force damage.
If more than two d20s are rolled (e.g., Elven Accuracy), doubles trigger if any two match. If multiple triggers apply, add this damage only once per hit.

Re-targeting. On later turns, you may use a bonus action to move this enchantment to another willing creature within range.

Gambit (d8)
1 — Backfire: The target takes 1d8 psychic damage and gains no bonus from this spell this round.
2 — Cold dice: No bonus from this spell this round.
3–6 — Stacked: Base effect only.
7 — Hot table: Every hit the creature makes this round deals the bonus damage (no doubles required).
8 — Eights wild: In addition to the base effect, the bonus also triggers when any d20 rolled for the attack shows an 8 (includes 18).

At Higher Levels. When you cast this spell using a slot of 3rd level or higher, choose one enhancement per slot level above 2nd (you may pick the same enhancement multiple times for this casting):
• Raise the payout: Increase the bonus die one step (d8 → d10 → d12).
• Spread the stack: Affect one additional creature; all affected creatures share the same Gambit roll each round.
• Tilt the table: The bonus triggers on any hit made with advantage, even without doubles. If you choose this enhancement a second time, the bonus triggers on any hit. (Max twice.)