Today’s Dungeons and Dragons magic item comes from advice I’ve read on line (from SlyFlourish?) about having a high level dragon’s ability to ignore spells be something visible. Here, then, is the Gem of Magic Absorption
Gem of Magic Absorption
Wondrous Item, Rare, Attunement
Once a creature attunes to this gem, it may toss the gem in the air. The gem begins circling the creature’s head. When a spell is cast at the creature, it may decide to have the gem absorb the spell. Once a gem has absorbed a spell, it cannot do so until at least twelve hours have passed. It remains circling the owner’s head but is dull (the owner may voluntarily stop it from circling its head and grab it at any time, whether it has absorbed spells or not). For each level of the spell absorbed (based on spell slot used), there is a 1% chance the gem is destroyed.
Certain high level creatures (dragons and others?) can use the gem to absorb up to three spells per day. Gems used by these creatures cannot be destroyed. Anti-magic or other spells do NOT cancel this items ability to absorb spells. If an attuned creature dies, there is a 50% chance the gem is destroyed. That and spell absorption are the only known ways to destroy a gem.
Don’t forget to check out my items on DMs Guild!