The Mourningstar is a craftable post-Moon Lord flail and is the direct upgrade of the Solar Eruption. Similarly to the Solar Eruption, the Mourningstar fires two solar spear-like projectiles that extend and retract from the player's position, following a narrow arc in the general area of cursor for the duration of their travel. The flails have infinite piercing capabilities, ignore tiles, and create explosions when hitting enemies. Both the flails and the explosions created inflict the Daybroken debuff on hit enemies.
Its best modifier is Godly.
- Despite firing two projectiles, only one is visible at a time, and the other can only be seen from the dust it leaves behind.
- The Mourningstar cannot destroy Cobwebs. It shares this trait with the Nebulash and Cosmic Discharge.
- Mourningstar's name is a pun on the term "Morning Star", a name given to certain pre-sunrise sky objects or to a type of spiked mace, and the word "mourning", which means to grieve over someone's death.