Empress of Light

The Empress of Light is a Hardmode, post-Plantera boss fought in The Hallow. While she can be fought as soon as Plantera is defeated, she is significantly more difficult than most Hardmode bosses and will typically require post-Golem gear. The Empress of Light fight is optional and is not required for progression.

Summoning
The Empress of Light is summoned by killing a Prismatic Lacewing, a rare critter that spawns in the surface Hallow at night between 7:30 PM - 12:00 AM once Plantera has been defeated in the current world. The Prismatic Lacewing is one of the few entities that can be detected by the Lifeform Analyzer.

The Prismatic Lacewing can be killed at any time in any biome to summon the boss, however outside of the Hallow biome, the Prismatic Lacewing will disappear almost immediately, requiring the player to use persistent or quick weapons to kill it.

Although the Prismatic Lacewing only spawns naturally in worlds where Plantera has been defeated, it is possible to bring one to a Pre-Hardmode world and kill it to summon the boss.

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

Behavior
If fought during the day, the Empress enters an "enraged" state, indicated by the color of attacks turning a bright yellow. While enraged, all of her attacks instantly kill the player regardless of equipment. See below for exceptions.

If night falls (7:30PM) when fought during the day and she is not defeated, she will vanish and drop nothing.

If fought in Expert or Master Mode, she will always use her enraged attack pattern, but without the massive damage increase.

Attacks

 * Prismatic Bolts - Summons a cloud of prismatic bolts that home in on the player after a short delay. These bolts do not have perfect tracking, and will miss if the player makes a sharp turn as they approach.
 * Prismatic Bolts 2 - Fires prismatic bolts in a clockwise spiral, which behave identically to those used in the first variant of the attack. This version is harder to dodge, and when she is enraged she summons more bolts.
 * Dash Attack - Positions herself to the left or right of the player before charging horizontally in the player’s direction. This attack is additionally preceded by a sound effect and several images of the Empress spinning around her right before she dashes. She briefly becomes invincible during the attack, removing any Daybreak spears attached to her and marks from whips.
 * Sun Dance - Hovers above and slightly to the left of the player and emits 6 persistent rays of light (8 if enraged) that slowly rotate clockwise around her. 3 sets of rays are created per sun dance, each positioned slightly further clockwise than the last.
 * Everlasting Rainbow - Releases a ring of 13 stars that slowly spiral out clockwise from her original position, then spiral back inward in the same direction. These stars leave behind a trail of light that will damage the player.
 * Ethereal Lance - Summons a swarm of swords that launch in the direction the player was headed when they were summoned, telegraphed by colored beams. These swords are summoned behind where the player was moving, or all around the player if they were stationary. The swords do no damage until launched. If enraged, extra swords are summoned, and they will launch faster.
 * Ethereal Lance 2 - Summons four evenly spaced waves of swords that travel across the screen, telegraphed by colored beams. The first wave travels from the left side of the screen to the right, the second from right to left, the third wave from top-left to bottom-right, and the fourth wave from top-right to bottom-left.
 * If enraged, there will instead be six waves of swords that target specific points around the player instead of traveling from one side of the screen to the other. The first wave travels from the left side of the screen to the right of the player, the second wave from the right side to the left of the player, the third wave from top side to the bottom-right of the player, the fourth wave from top side to bottom-left of the player, the fifth wave from the bottom side to top-right of the player, and the sixth wave from the bottom side to top left of the player.

Attack Pattern
The Empress has set attack patterns for both of her phases.

First Phase
When spawned, the Empress will hover in place for a few seconds before executing the following attacks in order: This sequence of attacks repeats indefinitely until the second phase starts.
 * 1) Prismatic Bolts
 * 2) Dash Attack
 * 3) Sun Dance
 * 4) Dash Attack
 * 5) Everlasting Rainbow
 * 6) Prismatic Bolts
 * 7) Dash Attack
 * 8) Ethereal Lance
 * 9) Dash Attack
 * 10) Everlasting Rainbow

Second Phase
When the Empress is below half of her max health, she will disappear for a second then reappear above the next estimated location of the player, adopting a new appearance before executing a new set of attacks, with slightly shorter attack intervals than before: This sequence of attacks repeats indefinitely until she is defeated.
 * 1) Ethereal Lance 2
 * 2) Prismatic Bolts
 * 3) Dash Attack
 * 4) * If enraged, she will cast a modified version of Ethereal Lance after the dash before resuming her normal pattern (targets where the player is rather than where they will be)
 * 5) Everlasting Rainbow
 * 6) Prismatic Bolts
 * 7) Sun Dance
 * 8) Ethereal Lance
 * 9) Dash Attack
 * 10) Prismatic Bolts 2

Tips

 * To avoid accidentally summoning the boss, use the Guide to Critter Companionship, which prevents the player from damaging critters including the Prismatic Lacewing.
 * Consider using a Bug Net to capture any Prismatic Lacewings rather than killing them immediately. This will allow the player to easily fight the Empress at a proper time and place once prepared.
 * Although the Prismatic Lacewing can only spawn at night, the Empress of Light can be spawned at any time of day using captured Prismatic Lacewings.
 * If the Prismatic Lacewing is released outside of the Hallow, it will disappear very quickly. This can be circumvented by placing the Lacewing directly into a stationary area-of-effect projectile, such as a Clinger Staff's flame pillar or a Rainbow Gun's rainbow.
 * A Rod of Discord, dropped from Chaos Elementals, will help the player dodge some of her attacks.
 * If attempting to fight the Empress during the day to obtain the Terraprisma, defense and damage resistance should be completely disregarded in favor of damage, dodges, and mobility, as any damage taken will be beyond lethal regardless.
 * The damage cancelling effect of the Master Ninja Gear, Brain of Confusion, and Hallowed armor can allow the player to occasionally take hits without instantly dying.
 * The dash ability from Shield of Cthulhu, Master Ninja Gear or Solar Flare armor can increase mobility.
 * Using wings with hover or fast acceleration capabilities, such as Fishron and Betsy's Wings, or the Jetpack can be quite effective for dodging due to their high speed and acceleration.
 * If using the Rod of Discord during her daytime fight, use it freely while ignoring the Chaos State debuff. Losing a fraction of health to Chaos State is far better than losing all of it to one of the Empress's attacks.
 * A riskier strategy would see the use of flying Mounts instead of wings or boots, which would free up equipment slots for increased damage output.
 * Use weapons that are capable of dealing damage reliably from long range, such as the Blizzard Staff, Possessed Hatchet, Chain Gun, or Tactical Shotgun with Chlorophyte Bullets.
 * A large arena constructed of Asphalt Blocks and layers of platforms is highly recommended, especially with the demand to mobility whilst fighting the Empress during the day.
 * For fighting the Empress during the day, these arenas do not require boosting structures, such as Campfires or Heart Lanterns, as instant death negates their regeneration buffs.
 * She is not immune to any practical debuffs. This can be a good extra source of damage, especially with the use of Ichor, Betsy's Curse, or Daybroken.
 * It is best to stay at an average level or below the Empress of Light as she zips above the player's position after every attack she does making it lethal in daytime and/or damaging at night.

Trivia

 * This boss was described as "a beautiful bullet hell" by Cenx before 1.4 was released.
 * Crowno has confirmed that the Empress is inspired by the Japanese video game series  and other bullet hell games. One can see the inspiration clearly in her attack patterns and her music.
 * The Empress of Light is one of 6 bosses with exclusive music, the others being Queen Slime, Plantera, Duke Fishron, Moon Lord, and Queen Bee.
 * Seeing as she can deal tens of thousands of damage during her day form, she is the first enemy in the game to be stronger than Dungeon Guardian in terms of raw attack damage.
 * However, the Dungeon Guardian still holds the title as the toughest enemy in the game, because of its 9999 defense.
 * The Empress of Light is one of 3 Hardmode bosses that are not necessary for game progression. The others are Queen Slime and Duke Fishron.
 * She is the only nocturnal boss that uses upgraded moves rather than just one move when enraged.
 * Several sound effects used by the Empress of Light appear to be samples of the "Whale Probe's" communications from the 1986 American science fiction movie .
 * The Empress of Light's light effect during spawn is internally named DeathAurora.
 * The codename of Empress of Light is HallowBoss.
 * Crowno has stated that the V-shaped line beneath the Empress' eyes, which some players may mistake for a mouth, is actually her nose.
 * The Empress of Light is one of the only boss fights that consists of a single destructible entity, the other being the Deerclops.
 * All other boss fights have either multiple bosses, multiple segments or boss minions that play a part in their boss fights.


 * This suggests that the Empress sees the player as impure after they have killed the Prismatic Lacewing.
 * This may mean that the Empress of Light is the Ancient Spirit of Light mentioned in the official lore.