Vitamins

Vitamins are a Hardmode accessory that provides immunity to the Weak debuff. The item has a /  chance to drop from Corruptors and Floaty Grosses, which are encountered in the Cavern Corruption/Crimson.

Vitamins are one of the ingredients required to make the Armor Bracing, which is a crafting material required to make the Ankh Charm, an accessory further required to make the Ankh Shield.

Trivia

 * The image on the jar appears to be a flexing arm, representing the Vitamin's abilities to fight off weaknesses and provide strength.