Star

Stars (or Soul Cakes during Halloween and Sugar Plums during Christmas) are common powerups that can be dropped by any enemy (8.3% if you are below max mana). It is not an inventory item, but is instead instantly consumed and restores 100 mana. Stars are as common as Hearts, but only drop when a nearby player is below full mana.

It is also possible to spawn Stars (and their seasonal counterparts) with a Star Statue.

They can be collected within range of 2 blocks which can be increased with Celestial Magnet and its upgrades.

Trivia

 * Soul Cakes are likely a reference to an older Halloween tradition called soul cakes, which is a small round cake which is traditionally made for All Saints Day or All Souls' Day to honor the dead. They were often simply referred to as souls, and were given out to children and the poor (known as soulers), who would then go from door to door on Halloween singing and saying prayers for the dead. Each cake eaten would represent a soul being freed from purgatory. The practice of this is often seen as the origin for modern trick-or-treating.
 * Although mana stars are instantly consumed on pickup, it is possible to hack in mana stars into your inventory through the use of editors. The hacked-in mana stars still act like normal mana stars, and will still be consumed on pickup.

History
星星 Étoile