Empress of Light

The Empress of Light is a Hardmode Hallow boss summoned by killing a Prismatic Lacewing, a critter that appears at night in the Hallow. She can be fought in either normal or enraged form: at night she behaves normally, but during the day she becomes enraged and is far more dangerous. Although she is a Hardmode boss, she can be summoned in a pre-Hardmode world.

She is notable for being the only boss that enrages during the day and returns to a non-enraged state at nightfall. If she is not damaged during the night, she despawns when morning arrives; if she was damaged, she remains active until day begins, at which point she switches to her enraged state instead of leaving. Because of this, players trying to earn Terraprisma have only the same day they summon her to defeat her before night ends. In Remix and Zenith worlds, summoning her above the surface at night causes her to despawn immediately.

Her attacks are designed around fast movement and dense projectile patterns, and all damage from her attacks bypasses other invincibility frames. Ethereal Lance is especially important because it can target the player regardless of distance, with the lances appearing near the player rather than traveling from the boss. During her second phase, switching between normal and enraged attack sets can cause her to repeat a move or jump to a different point in the sequence.

• The Guide to Critter Companionship prevents accidental summoning by stopping the player from harming critters, including the Prismatic Lacewing.
• Catching Prismatic Lacewings with a Bug Net lets the player choose when and where to start the fight.
• If a captured Prismatic Lacewing is released outside the Hallow, it disappears quickly, so placing it into a stationary damaging area such as a Clinger Staff flame pillar or Rainbow Gun stream is an effective way to kill it on purpose.
• A Rod of Discord is useful for evading some attacks, and during the daytime fight its Chaos State debuff is worth accepting if it helps avoid lethal damage.
• For the daytime battle, survivability should be ignored in favor of mobility and damage, since any hit is fatal. Shield of Cthulhu, Master Ninja Gear, Solar Flare armor dashes, hover-capable wings, fast-acceleration wings, the Jetpack, and even flying mounts can all help.
• Large Asphalt arenas with layered platforms are recommended, especially for the daytime version of the fight.
• Campfires, Heart Lanterns, and Bast Statues are unnecessary, since taking any damage during the daytime fight kills the player immediately.
• Weapons that deal reliable long-range damage or have homing are preferred, such as Blizzard Staff, Possessed Hatchet, Scourge of the Corruptor, Tsunami, Aerial Bane, Snowman Cannon, Chain Gun, or Tactical Shotgun with Chlorophyte Bullets.
• She is not immune to practical debuffs, so effects like Ichor, Betsy's Curse, or Daybroken can add meaningful damage.
• Staying below or around her vertical position is often safer, since she tends to move above the player after each attack, making contact damage more likely.

The Empress of Light is also unusual in several technical and design respects. She is one of only two bosses made of a single destructible entity, the other being Deerclops. Her internal name is HallowBoss, and her spawn effect is internally named DeathAurora. She was described during development as a “beautiful bullet hell,” and her design draws inspiration from Japanese shoot-’em-up games.