This small piece of mirror fits nicely into the hand, the edges having been polished and ground smooth over the many hundreds of years of its existence. The reflective surface holds no fingerprints or other smudges, and even dust will not settle onto it. It was once part of a large mirror, forged by the gods themselves, but subsequently shattered during their last great war (or perhaps just during an altercation between a few of them). There are more shards scattered about the planes of reality, but no one knows for sure how many. It is rumored that each shard contains only a portion of the power that the great mirror once held - each shard granting different abilities.
Once per duration* the wielder can use an interrupt/reaction to use the shard to retarget a spell being cast at them. This only works on spells with a single target, and the new target must be valid or the spell fails to have any effect.
As an added bonus, the mirror shard cannot be the target of any spells.
*duration - up to the DM/GM's discretion. Could be daily, weekly, following the cycle of the moon, etc.
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