Clamshell of Pleasantries
Wondrous Item, uncommon (requires attunement)
Legends speak of this magical clamshell ornament being created by the sea elves or the tritons for their encounters with hostile humanoids of the deep, or their difficult dealings with 'surface-dwellers'.
The legends actually tell the reverse of the truth: this item was crafted by a sahuagin exiled by his people for being too friendly. He used the shell in order to deal with those that would normally attack him on sight, to make a good first impression – which rarely lasted.
Unfortunately the sahuagin grew so reliant on his magical clamshell that any friendliness he was forced to show or was shown by those he encountered, real or magical, soon filled him with nausea and anger, and he eventually a cranky old hermit.
Once attuned, the bearer may cast charm person as a first level spell up to three times per day using only a material component – the caster opens and consumes the raw flesh of the clam, which regrows every dawn.
The flesh of the clam is always sour and unpleasant to eat.
Curse: Part of the creator's spirit lingers in the item – over a short time, friendliness and camaraderie annoy the bearer, though they will still use the clam at the first opportunity (or opportunities) each day.
Insight and Persuasion checks are made with disadvantage, and the character always smells faintly of rotting fish.
If any raw clam flesh remains uneaten, it will spoil. Regardless, shortly before dawn the attuned character feels a compulsion to consume it so that fresh flesh can regrow.
Credit: Wikipedia user febb