Empress of Light

The Empress of Light is a Hardmode, post-Plantera boss. While she can be summoned as soon as Plantera is defeated, she is significantly more difficult than most Hardmode bosses and will typically require post-Golem gear. Fighting the Empress of Light is completely optional and not required to progress. However, her defeat will reward the player with powerful weapons.

Summoning
The Empress of Light can be summoned by killing a Prismatic Lacewing, which is a rare critter that spawns in the surface Hallow during the night. As it is a rare creature, it can be detected by the Lifeform Analyzer. The Prismatic Lacewing must be killed during nighttime to summon the boss.

Like all critters, the Prismatic Lacewing can be caught with any bug net, which can then be released, and killed, by the player manually.

However, attempting to kill the Lacewing during daytime will instead just kill the critter, and will not summon the boss.

Behavior

 * The boss uses fast-paced multicolor attacks. She has two attack patterns: In the first stage, she will alternate between various attacks in which multiple projectiles home in on the player. In the second stage, she will fire projectiles across the screen in straight lines at various angles.
 * If she is fought during the day, all of her attacks will deal massive amounts of damage, killing the player instantly. If the Empress is killed during the day, she will drop the Terraprisma.

Tips

 * It would be wise to defeat Golem first, so the Cosmic Car Key will become available.
 * Not only does the Empress have to be killed during the day to gain the Terraprisma, but all damage she receives must be during the day as well. Any attack from the Empress during the day will instantly kill the player.
 * Consider using a Bug Net to capture any Prismatic Lacewings when you see them, rather than killing them immediately. This will allow you to easily fight the Empress at a time of your choosing once you are prepared. Note that if the Prismatic Lacewing is released outside of the Hallow, it will immediately disappear.
 * While they immediately disappear, it is still possible to kill the Prismatic Lacewing outside of the hallow. This is done by having a weapon selected, placing the Lacewing from your inventory, then spamming left-click so that you immediately attack, killing it in time to spawn the boss.
 * If she is fought in the daytime, she will use that a new attack that is an insta-kill.

Trivia

 * This boss was described as "a beautiful bullet hell" by Cenx before 1.4 was released.
 * She is similar to Skeletron Prime in that she gains increased damage during the day. However, Skeletron Prime does not drop items when defeated at daytime, unlike the Empress of Light.
 * The Empress of Light is one of the two new bosses added in the 1.4.0.1 update, the other being Queen Slime.
 * She and Plantera have the only musical instrument drops of any boss, with The Axe and the Stellar Tune having the same drop chance as well.
 * The Empress of Light is one of 5 bosses with exclusive music, the others being Queen Slime, Plantera, Duke Fishron and Moon Lord.