Calamity Mod Wiki
Astrum Deus
Astrum Deus.png
TypeBossBurrowing Enemy
EnvironmentAstral Infection
AI TypeAstrum Deus AI
Max Life562,500 / 900,000 / 1,080,000 (total)
KB Resist100%
Inflicts debuffExtreme GravityExtreme Gravity
100% chance
Debuff durationInfinite
Debuff tooltipYour wing time is reduced by 50%, infinite flight is disabled
Immune toAll debuffs except:
EnragedShellfish ClapsKami Flu
Coins20 Gold Coin
Astrum Deus map.png
Map Icon

Astrum Deus Trophy.png "A star-spawned horror tunnels through the astral infection." Astrum Deus Trophy.png

Not to be confused with Astrum Aureus, a similarly-themed cyborg boss.

Astrum Deus is a Hardmode boss that must be defeated in order to allow Astral Ore to be mined. It begins as a large worm, similar to The Destroyer, but splits later in the fight.


Astrum Deus does not spawn on its own and can be summoned by using the Astral Beacon with a Titan Heart or Starcore in the inventory at night. Astrum Deus can be spawned even in early Hardmode with Titan Hearts, but the boss is intended to be fought after the Lunatic Cultist has been defeated. When successfully activated, two astral stars rise from the beacon and eventually combine to summon Astrum Deus.


Astrum Deus Head
Astrum Deus Head.png
TypeBossBurrowing Enemy
AI TypeAstrum Deus AI
Damage120 / 240 / 268 / 280
Max Life187,500 / 300,000 /
KB Resist100%
Inflicts debuffAstral Infection (debuff)Astral Infection (debuff)
100% chance
Debuff duration3 seconds
Debuff tooltipYour flesh is melting off
Astrum Deus Body
Astrum Deus Body.png
TypeBossBurrowing Enemy
AI TypeAstrum Deus AI
Damage100 / 160 / 192 / 200 (Contact)
90 / 152 / 176 / 188 (Astral Laser)
120 / 180 / 208 / 224 (Astral Mine)
Max Life187,500 / 300,000 /
KB Resist100%
Inflicts debuffAstral Infection (debuff)Astral Infection (debuff)
100% chance
Debuff duration2 seconds (Contact/Astral Laser)
5 seconds (Astral Mine)
Debuff tooltipYour flesh is melting off
Astrum Deus Tail
Astrum Deus Tail.png
TypeBossBurrowing Enemy
AI TypeAstrum Deus AI
Damage80 / 128 / 160 / 168
Max Life187,500 / 300,000 /
KB Resist100%
Inflicts debuffAstral Infection (debuff)Astral Infection (debuff)
100% chance
Debuff duration1.5 seconds
Debuff tooltipYour flesh is melting off


Astrum Deus behaves similarly to worms, burrowing through the ground and attempting to ram the player, with the additional ability to fire lasers at the player from its segments. As the fight progresses, however, it gains the ability to fly (similarly to Wyverns) and, after it reaches half health, splits into two smaller worms with the same abilities as the original. Once one of the smaller worms is killed, the other despawns and the fight ends. Astrum Deus has 51 / 61 / 71 / 81 segments before splitting, and each worm created from it splitting has 26 / 31 / 36 / 41 segments. All of its attacks inflict the Astral Infection debuff.

If Astrum Deus is alive when it becomes daytime, it will enrage, greatly increasing its movement speed.


  • Astrum Deus burrows through the ground, attempting to ram the player when it approaches them from below.
    • If the player is far enough from the ground, Astrum Deus will swim through the air to reach them.
    • If Astrum Deus is far away from the player, it will gain a massive speed boost until it is close to them.
    • Astrum Deus’ speed increases as its life decreases.
  • Every 10 seconds, Astrum Deus fires lasers from its body in a stream starting from its head and ending at its tail.
    • The rate at which these lasers are fired staggers as the fight progresses, causing the attack to last longer the longer the fight progresses. Given enough time, Astrum Deus will constantly fire lasers at the player.
  • When Astrum Deus reaches 80% life, every 15 seconds, it will alternate between burrowing like a worm and flying like a Wyvern.
    • While Astrum Deus is flying, segments close to its tail will leave behind astral mines instead of firing lasers, which lingers in place for 15 seconds before exploding. The lower Astrum Deus’ life is, the more segments will leave mines.
  • When Astrum Deus reaches 50% life, it will split into two smaller worms, which act the same as the original, with some differences:
    • One worm starts off flying, while the other starts off burrowing. They both alternate between the two behaviors every 10 seconds. The one that is currently flying will be blue, and the one that is currently burrowing will be green.
    • Worms that are currently flying will only leave behind astral mines instead of firing lasers.
    • The staggered fire rate of the lasers and mines for each worm is reset.
    • One of the worms has a slightly shorter delay between its laser barrages.

In Expert Mode[]

  • Number of segments increased from 50 to 61 before splitting, and from 26 to 31 after splitting.
  • Segments can fire independently from laser barrages after they take enough damage.
  • Before splitting, only the damaged segments noted above can leave behind mines.
  • Mines and laser barrages are fired every 4 seconds after it splits instead of 10.

In Revengeance Mode[]

  • Number of segments increased from 61 to 71 before splitting, and from 31 to 36 after splitting.
  • Movement speed is increased.
  • Independently firing segments have an increased rate of fire.
  • All nearby players are inflicted with Extreme Gravity.

In Death Mode[]

  • Number of segments increased from 71 to 81 before splitting, and from 36 to 41 after splitting.
  • Movement speed is further increased.
  • Can fly at any time before splitting, and only leaves mines instead of firing lasers while flying.
  • While burrowing, the head will make sharp turns to hit the player if it is close to them.



  • All Astrum Deus segments take reduced damage from non-minion piercing projectiles in Expert Mode. Projectile damage is divided by the number of times it pierces. Infinite piercing deals 50% damage.
  • All segments reduce damage from grenade-type projectiles by 80%. A list of affected projectiles is below.
Resisted grenades
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  • All of Astrum Deus' loot will spawn at the nearest segment with the exception of 5-15 of the Stardust and the Hearts, which will always spawn at the head.
  • Astrum Deus takes 99% less damage from all sources for the first 10 seconds after it spawns, and for the first 10 seconds after it enters Phase 2.
  • If Astrum Deus is killed before splitting into two, it will drop 5-15 stardust, some hearts and mana, but no Treasure Bag. It will not split after this, and the boss will need to be re-summoned. The player will not be able to mine Astral Ore.
  • Repeatedly killing Astrum Deus can be a good way to get Fallen Stars to use as ammo for weapons like the Starmada or Starfleet.


For more elaborate strategies on defeating Astrum Deus, including weapon and arena recommendations, see Guide:Astrum Deus strategies.
  • Try and keep moving, and don't stay in one spot. Avoid circling the boss as the astral orbs will make it too difficult to do so.
  • Be aware of the position of the mines as they can wall off the player, making it extremely difficult to break out and leaves the player as easy prey.
    • During Phase 2, the trail of mines will be shorter, although there will be more trails left throughout the arena.
      • Having a large arena can make this much less of an issue.
  • Astrum Deus’ abundance of projectiles can, especially on less powerful computers, cause large frame rate drops. This can be used to the player's advantage by turning frame skip off, giving them more time to process and dodge attacks.
  • Like several other bosses, Astrum Deus will not despawn no matter the distance the player travels from it. This means the Magic Mirror can be used to teleport to a more suitable spot to fight.


  • Astrum Deus' theme is Pest of the Cosmos, which was composed by the artist DM DOKURO.
    • If the Calamity Music add-on mod is disabled, Boss 3 will play instead.
  • "Astrum Deus" in Latin roughly translates to "The Star God".
  • Astrum Deus used to be spawned by killing three Atlases after the Lunatic Cultist was defeated.
  • In previous versions of the mod, the fight consisted of one larger worm with ten smaller worms as minions.
  • If the Boss Checklist Mod is installed, its unique despawn message will be "The infected deity retreats to the heavens."


Since ancient times, humans have looked to the skies with admiration and wonder; countless religions place their gods and their heavens amongst the skies. The sun was their god of warmth and life, banishing the darkness and offering hope. The moon was an idol amidst the night - a symbol of light, yet a beguiling one that beckoned with madness.

The stars, they once said, were no single gods. The wondrous stream of stars that stretched across the sky on cloudless nights - the source of those lights was a divine serpent of incomprehensible proportions. Its very nature was unimaginable, to the point that its presence in their reality could only be glimpsed through the countless stars its body birthed. As the collective faith of humanity gathered, it gave rise to the manifestation of their belief: a true god of the stars, soaring through the cosmos.

But even gods could be laid low. Conquering the land countless years after the god of the star's legend was born, the Jungle Tyrant looked to the skies and saw yet another realm to dominate - beginning by striking down Astrum Deus with his own Devourer of Gods. Empowered by those it had already consumed, the Devourer tore open the larger divine serpent’s gut and burrowed in, feasting on its body and killing it from the inside out before crushing its husk to pieces between its coils and scattering the remains to the cold void of space.

In ancient times, it was said that the god of the stars would descend upon the planet in its last days. Its body would infuse the earth with astral power and transform lesser lifeforms into its guardians. The power lingering in its corpse attracted worms to itself, empowering them so that they may grow - and Astrum Deus may one day return to the cosmos. Even when torn asunder, the god's corpse held power; just as the legend that gave rise to it claimed, those fragments of its body would one day fall to the planet and choose a successor to the god of the stars.