Nightglow

The Nightglow is a Hardmode, post-Plantera magic weapon that has a chance to be dropped by the Empress of Light. When fired, four rainbow crystals emerge from the player and home in on nearby enemies.

Each of the rainbow crystals can pierce enemies and hit three times, resulting in high potential damage, but lose 20% of damage for each enemy struck. However, since they spawn in random directions from the player and are destroyed if they collide with obstacles, it can be difficult to use this weapon in confined spaces.

Trivia

 * It can be considered an indirect upgrade of the Spirit Flame, a magic weapon that also spawns homing magic projectiles around the player.
 * As the weapons that the Empress of Light drops are based on her attacks, the Nightglow seems to be based off of her Prismatic Bolts.