Master's Crown (5e Equipment)
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Wondrous Item, legendary (requires attunement)
A tin gold band of a crown with what seems to be a gem embedded in the center. One of two items that can be given by a tricky warlock who tells an odd riddle.
When you become attuned to this crown, choose one of your ability scores. While wearing this crown, that ability score increases by 4, as does your maximum for that score, and you add your proficiency bonus to any ability check or saving throw using that ability, even if it has already been applied; however, each of your other ability scores becomes 10 unless it is already lower.
Becoming attuned to the jack's foot breaks your attunement to this item.