Master Sword

The Master Sword is a Hardmode sword. It is sold by the Storyteller for after Skeletron Prime has been defeated.

By holding down, you can store up energy in the weapon, up to a maximum of 50. This increases the attack power of the weapon, and allows it to temporarily shoot energy until it runs out of power, after which you'll need to charge it up again.

Trivia

 * The Master Sword is a reference to the Master Sword from the Legend of Zelda. Unlike Elements Awoken's Master Sword, the Master Sword from the Legend of Zelda is usually able to shoot sword beams when the user is at full health, though aside from this it acts the same as a regular sword.
 * Charging energy in the sword may be a reference to The Legend of Zelda: Skyward Sword, in which you can hold your sword to the sky for a second, charging it up and allowing you to fire a single sword beam no matter what health you are at.