Battlefate

Choose one creature you can see within 30 feet of you as the spell’s target. At the start of each of its turns until the spell ends, the target gains a d4 fate die. During that turn, when the target makes an an attack roll, ability check, saving throw, or damage roll, it can choose to roll the fate die and add the result to the total for that roll.

If the target ends its turn with an unused fate die, it must roll the die immediately, gaining a bonus to its armor class equal to half the result. This bonus ends at the start of its next turn.

If a creature would have ever have more than one fate die (such as from multiple castings of this spell), it chooses only one of the fate dice to keep; the others are lost.

At Higher Levels. The fate die increases when you cast this spell using a higher-level spell slot. With a 3rd or 4th level slot, the die increases to a d6. A 5th or 6th level slot increases the die to a d8. A 7th or 8th level slot increases the die to a d10. A 9th level slot increases the die to a d12.

Original Source: The Blackstaff's Book of 1000 Spells, page 51.