Calamity Mod Wiki
Astrum Aureus
Astrum Aureus.png
EnvironmentAstral Infection
AI TypeAstrum Aureus AI
80 / 176 / 198 / 209
74 / 128 / 148 / 160 (pre-Moon Lord)
148 / 256 / 296 / 320 (post-Moon Lord)
80 / 140 / 160 / 172 (pre-Moon Lord)
160 / 280 / 320 / 344 (post-Moon Lord)
Max Life89,200 / 142,720 / 171,200 (pre-Moon Lord)
243,750 / 390,000 / 468,000 (post-Moon Lord)
KB Resist100%
Inflicts debuffAstral Infection (debuff)Astral Infection (debuff)
100% chance
Debuff duration1 second (Lasers)
2 seconds (Crystals)
3 seconds (Contact)
Debuff tooltipYour flesh is melting off
Immune toConfusedPearl AuraAstral Infection (debuff)Poisoned

Astrum Aureus Trophy.png "A titanic cyborg infected by a star-borne disease..." Astrum Aureus Trophy.png

Not to be confused with Astrum Deus, a similarly-themed worm-like boss.

Astrum Aureus is a Hardmode boss. Defeating it causes an Astral Infection meteor to fall somewhere in the world.

After defeating the Moon Lord, Astrum Aureus increases substantially in difficulty, with boosted health and damage, and drops a new mount.


Astrum Aureus does not spawn on its own and must be summoned at Night using the Astral Chunk in the Astral Infection biome.


When first summoned, Astrum Aureus will be in its recharging phase, indicated by the lack of astral flames. While recharging, Astrum Aureus deals no contact damage and has no defense. After several seconds, its flames will ignite and it will begin to attack the player, cycling through a specific attack pattern before re-entering its recharging phase and repeating the attack cycle. The time it spends in its recharging phase decreases as its life decreases. All of its attacks inflict the Astral Infection debuff.

If Astrum Aureus is alive when it becomes daytime, it will enrage, drastically increasing the speed it moves and jumps and completely removing its recharging phase.


  • Crawls toward the player, firing pairs of lasers at them. Astrum Aureus will fire eight laser blasts before transitioning to its next attack.
    • During this attack, Astrum Aureus can swim through blocks.
    • The number of lasers fired per blast increases as Astrum Aureus loses HP, up to 4.
  • Makes a far and tall jump towards the player. If the player moves under it, it slams down, changing its horizontal speed to try to land on them. When Astrum Aureus lands, it fires a laser blast at the player. Astrum Aureus performs this attack three times before returning to its recharging phase and repeating this attack cycle.
  • If Astrum Aureus is below 75% life, before returning to its recharging phase, it will instead stand still and fire two consecutive Astral CrystalAstral Flame Crystals upwards, then teleport close to the player. These Flame Crystals home in on the player after two seconds and, after three more seconds pass or they get close to the player, lose their homing ability and gradually accelerate, eventually flying off screen.
    • Astrum Aureus is in its recharging phase when it teleports, preventing it from hitting the player when it does so.
  • Below 50% HP, cycles through all attacks 50% faster.

In Expert Mode

  • Gains the ability to jump through blocks.
  • Gains movement and jump speed as its life decreases.
  • Time spent in its recharging phase decreased.
  • Starts firing sets of four Astral Flame Crystals at 80% life, which increases as Astrum Aureus loses life.
  • Below 40% HP, summons two Aureus Spawns before it teleports. Aureus Spawns float towards the player and fire homing Astral CrystalAstral Flame Crystals, occasionally teleporting to a random nearby location. However, after they are reduced to 60% life, they rapidly but loosely home in on the player, exploding after they hit the player or a solid block or after 10 seconds pass. Only 2 Aureus Spawns may be active at a time.

In Revengeance Mode

  • Movement speed is increased, increasing even more as its life decreases.
  • Gains jump height the further up the player is from it.
  • Time spent in its recharging phase decreases even further as its life decreases.
  • Fires many more Astral Flame Crystals.
  • Starts summoning Aureus Spawns at 80% HP.
  • Below 30% HP, starts making multiple short hops before jumping at the player.

In Death Mode

  • Starts off firing 3 lasers per burst, increasing up to 6.
  • Starts firing Astral Flame Crystals and summoning Aureus Spawn at 85% HP.
  • Loses 1% of its maximum HP every time it summons an Aureus Spawn.
  • Aureus Spawn now actively attack the player by firing additional homing Astral Flame Crystals.
  • Lasers are fired in much wider spreads.


Image Name Condition
Aureus Spawn Aureus Spawn In Expert Mode or in the Boss Rush



  • Be careful straying too far from it (such as flying too high altitudes), as Astrum Aureus will despawn if it cannot teleport to the player.


For more elaborate strategies on defeating Astrum Aureus, including weapon and arena recommendations, as well as a more in-depth breakdown of the fight, see Guide:Astrum Aureus strategies.


  • Moving in a semi-circle around Astrum Aureus while it fires lasers can help the player successfully avoid them.
  • The astral flame crystals gain increased velocity and homing capabilities the closer they are to the player, making it essential that the player keeps their distance from them until they launch away.
  • In Revengeance Mode, avoid damaging the Aureus Spawns. They are initially harmless and will only attempt to harm the player if they take enough damage.
  • Astrum Aureus can be fought at the start of Hardmode, although it is not recommended to fight until the player has decent post-Plantera gear as its fast speed, height, and attacks can be easily overwhelming if unprepared.
    • If the Rework Early Hardmode Progression configuration option is enabled, Astrum Aureus can be fought as soon as any mechanical boss has been defeated, due to it unlocking Mythril and Orichalcum, though still not recommended.
      • Should the player have the skill and patience to defeat it, they can obtain many powerful items from both the boss and its defeat.


  • Astrum Aureus's theme is Interstellar Stomper, which was composed by the artist DM DOKURO.
    • If the Calamity Music add-on mod is disabled, Boss 3 will play instead.
  • Astrum Aureus replaces a removed boss, the Astrageldon Slime, which was a boss that fought much like the King Slime but was twice as big and emitted lasers in bursts at the player.
    • Prior to Interstellar Stomper's implementation, Astrum Aureus's theme was Cosmic Disgust, which was originally intended for the Astrageldon Slime. This is why the theme's introduction contains a motif from The Slime God's theme.
  • Astrum Aureus's name roughly translates to "golden star" in Latin, although its name is actually a reference to an infectious bacteria named Staphylococcus aureus.
  • Astrum Aureus can be summoned as soon as Hardmode begins, as its summoning item only requires Fallen Stars and Stardust.
  • Astrum Aureus's design was inspired by Security Robot B.O.X. from Metroid Fusion, as both their appearance and movements are similar, and are also both cyborgs that have been infected by a space infection.
  • If the Boss Checklist Mod is installed, its unique despawn message will be "Astrum Aureus’ program has been executed. Initiate recall."


When the Astral virus first appeared in Terraria to warp the landscape around it, the site became a phenomenon of interest to Yharim himself. What destructive power, what force of chaos, could have made such drastic changes in a phage that it could assimilate nearly any material into something similar to its own molecular structure? Commissioning Draedon to research the pathogen, Yharim had him look for a method to take advantage of the virus’ virtually alchemic traits, to see if they could be harnessed to serve his needs. Of course, Draedon’s first step was to collect samples. To accomplish this objective, he decided to once more construct an automaton to do his bidding. Although his assistants were at his disposal, he decided against it, as the environment would clearly not be suitable for humans. However, his blunder was in underestimating the enslaving factor of the Astral virus. Even the circuit boards and metal of the great machine he had built to lumber across the infected landscape and bring back subjects, succumbed to the enslaving will of the pathogen. However, this was by no means a disappointment to Draedon. To him, this was a sign of great promise, showing that the extent of the virus’ power was not limited to organic beings. Finding no need for the great machine any longer, Draedon abandoned it. Now, it stays dormant in the Astral Biomes, only awaking to protect these infections from outside threats.