Catalyst/Astrageldon (2024)

Not to be confused with the Astragelgun, a hardmode flamethrower.


Catalyst/Astrageldon (2)

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Astral Infection

AI TypeAstrageldon AI
Damage160 / 220 / 246 / 275 / 480
Max Life105,000 / 156,000 / 200,000
KB Resist100%
Inflicts DebuffExtreme Gravity
Debuff tooltipYour wing time is reduced by 25%, infinite flight is disabled
Inflicts DebuffArmor Crunch
Debuff tooltipYour armor is shredded
Inflicts DebuffCatalyst/Astrageldon (5)Astral Blight
Debuff tooltipYour flesh is boiling away
Immune to

AstrageldonPhase 2

Catalyst/Astrageldon (11)

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Astral Infection

AI TypeAstrageldon AI
Damage160 / 220 / 246 / 275 / 480
Max Life145,000 / 217,500 / 336,000
KB Resist100%
Grants BuffZero Gravity
Buff tooltipInfinite flight time
Inflicts DebuffArmor Crunch
Debuff tooltipYour armor is shredded
Inflicts DebuffCatalyst/Astrageldon (14)Astral Blight
Debuff tooltipYour flesh is boiling away
Immune to


  • Item (Quantity)Rate
  • Astra Jelly(Catalyst) (15-25 / 20-29)


  • Astral Lash(Catalyst)


  • Influx Cluster(Catalyst)


  • Astral Transmogrifier(Catalyst)


  • Super Healing Potion (5-15)


  • Astrageldon Mask(Catalyst)


  • Astrageldon Trophy(Catalyst)


  • Astrageldon (Lore)(Catalyst)

    100% (first kill)

  • Music Box (Astrageldon Title)(Catalyst)

    100% (first kill)

  • Scythe of the Abandoned God(Flawless)


  • Treasure Pod(Astrageldon)


  • Astrageldon Relic


  • Divine Jello


"Such an existence that defies comprehension."

Astrageldon is a Hardmode superboss. It takes the appearance of a gigantic slime infected with the Astral Blight with a slew of different unnatural abilities.


  • 1 Spawn
  • 2 Behavior
    • 2.1 Attacks
      • 2.1.1 Phase 1
      • 2.1.2 Phase 2
    • 2.2 In Expert Mode
    • 2.3 In Revengeance Mode
    • 2.4 In Death Mode
    • 2.5 On the For the worthy seed
  • 3 Aftermath
  • 4 Summons
  • 5 Notes
  • 6 Resistances
    • 6.1 General resistances
    • 6.2 Specific weapon resistances
  • 7 Tips
  • 8 Trivia
  • 9 Lore


Astrageldon is summoned by using the Astral Communicator (dropped by Ascended Astral Slimes in the Astral Infection at any time) before defeating the Moon Lord in Astral Infection. If Astrageldon's first phase has been defeated prior, the item will automatically summon it in its second phase, with its first phase becoming spawnable through its alt function.

  • If Astrageldon has been defeated prior, it can be resummoned after defeating the Moon Lord.
  • With the Calamity's Vanities mod enabled, the item can be used in the mod's artificial Astral Blight biome.


When spawned, Astrageldon will slam down onto the ground from the sky, creating two waves of Catalyst/Astrageldon (34)Blighted Obelisks moving outwards in either horizontal direction. The boss will then cycle through a set pattern of attacks until reaching phase 2 upon reaching 1 health. Astrageldon will then transition into phase 2, losing its rocks, changing the background, conjuring a storm of clouds that form a circular arena, and inflicting the player with the Zero Gravity buff. The Zero Gravity debuff gives the player infinite flight and remains for the duration of the fight. The arena deals damage to the player if touched, and will inflict them with the Interstellar Corruption debuff. Once the second phase is defeated, the boss performs one final attack, then explodes, dropping its loot. Talking to the Nurse while the boss is alive will summon a large meteor that will likely kill the player in a single hit.


Phase 1

  • Attempts to jump towards the player, similarly to most other slimes.
  • Jumps into the air, creating a harmless beam telegraph underneath it that acts as an indicator for where it's about to strike, then slamming downwards, creating two parallel waves of Catalyst/Astrageldon (35)Blighted Obelisks. This is repeated two more times before transitioning to its next attack.
  • Gains flight then starts hovering at a position diagonally upwards from its target. Astrageldon will then create 6 stars in an even pattern around itself, which shortly burst into 3 lasers each outwards. This is repeated two more times before transitioning to its next attack.
  • Repeatedly jumps in place, flinging Nova Slimes into the air while creating more Catalyst/Astrageldon (37)Blighted Obelisk waves each time it strikes the ground, then jumping upwards and offscreen. Nova Slimes then start raining down in waves, using the same choreographed beams that Astrageldon uses to mark where they are about to land. After all the slimes have been sent down, Astrageldon will then create its own choreographed beam and slam downwards, re-entering the fight.
  • Repeats its ground slam attack three more times.
  • Gains flight and creates two rotating asteroid belts composed of Catalyst/Astrageldon (38)Blighted Stones to orbit around itself while trying to position itself near the player. After this attack is finished, the cycle repeats.

Phase 2

  • Starts off by losing all of its Catalyst/Astrageldon (39) rocks then flinging them at the player, then creating a swarm of 4 pairs of Catalyst/Astrageldon (40)Nova Slimers and jumping upwards offscreen. Each pair of Nova Slimers will take turns creating choreographed beams to indicate they are about to attack, then slamming into each other, killing themselves and inflicting Interstellar Corruption if the player is caught within the blast. When most of the Nova Slimers have killed themselves, a large amount of horizontal choreographed beams will start spawning in the arena going upwards, and Astrageldon will appear again, then start rapidly dashing through all of them, going from the bottom of the arena upwards while creating Catalyst/Astrageldon (41)Nebula Residue. This attack is only performed once.
  • Tries to slam downwards onto the player several times while shooting out evenly spaced stars in a floral pattern that curve outwards.
  • Turns into its nebula form then leaves the arena. Astrageldon will then create a choreographed beam and dash into the player while creating star mines that detonate into a choreographed grid-like pattern. Astrageldon will then repeat this several times, with each use making the arena grow smaller.
  • The arena returns to its normal size and Astrageldon starts firing Catalyst/Astrageldon (42)Nebula Residue directly at the player while occasionally firing a bending floral pattern of 16 stars towards the player.
  • Slams downwards and creates 6 pairs of Nova Slimers. The attack plays out similarly to the first wave, but Astrageldon will create vertical choreographed beams instead of horizontal ones, then dash up and down them while moving horizontally instead of vertically.
  • Rapidly fires out a stream of stars that home in on the player. This is repeated once, then it will start over its attack cycle, but with some alterations.
  • After using its grid mine attack once-more, the arena will grow in size, Astrageldon will gain 50% damage reduction for a total of 60%, and then slam into the middle of the arena. Eight harmless yellow lines will then be emitted from Astrageldon, which then curves, creating a star pattern of yellow deathrays. The deathrays then rotate while Astrageldon occasionally unleashes floral patterns of 4 stars. Astrageldon’s damage reduction goes back to normal after this attack is finished.
  • After using its star barrage attack again, Astrageldon will begin to fire clusters of 5 condensed Catalyst/Astrageldon (43)Nebula Residue that explode into more residue outwards. Astrageldon will also occasionally release a floral pattern of 4 stars during this.
  • Once the boss reaches critical health, it will become invincible, position itself in the middle of the arena, then start spawning largeCatalyst/Astrageldon (44)Blighted Asteroids. The asteroids detonate into harmless yellow lines that are followed by damaging stars. The arena slowly closes in on Astrageldon while this attack is happening. Eventually meteors will stop raining down, and the arena will close in on Astrageldon and the boss will create a harmless explosion and drop its items.

In Expert Mode

  • Phase 1 health increased to 156,000. Phase 2 health increased to 217,500.
  • Damage increased from 160 to 220.
  • All slams in phase 1 now create rocks upon reaching 40% life. These rocks will rise from where Astrageldon lands, then quickly launch towards the player.
  • Shockwaves travel for 20% longer.
  • Creates 8 spokes of stars instead of 6 during phase 1 star attacks.
  • Summons 1 more Nova Slime per wave of Nova Slimes.
  • Creates 8 spokes of stars instead of 6 during star slams and Nebula Residue chase.
  • Creates 6 spokes of stars instead of 4 during Nebula Residue Mine attack.
  • Summons two additional pairs of Nova Slimers for a total of 6 initial pairs and 8 pairs on subsequent waves.

In Revengeance Mode

  • Phase 1 health increased to 200,000. Phase 2 health increased to 336,000.
  • Damage increased to 246.
  • Has time-based damage reactive damage reduction in phase 2.
  • Phase 1 now has a new attack which occurs after its Nova Slime rain where Astrageldon will jump, fire a floral pattern of stars, then slam downwards while chasing the player. This occurs three times before transitioning to its Asteroid Belt attack.
  • Shockwaves travel an extra 10% longer.
  • Creates 10 spokes of stars instead of 8 during phase 1 star attacks.
  • Phase 1 slams spawn rocks upon reaching 50% life instead of 40%.
  • Fires 1 extra Nebula Residue Mine every time it shoots for a total of 6 Mines.

In Death Mode

  • Damage increased to 275.
  • Shockwaves travel an extra 10% longer.
  • Phase 1 laser attacks shoot out 12 spokes of lasers instead of 10.
  • Summons 1 more Nova Slime per wave.
  • Slams create rocks upon reaching 75% life instead of 50%.
  • Summons an additional pair of Nova Slimers on subsequent waves for a total of 10 pairs.

On the For the worthy seed

  • Phase 2 immediately behaves as if two cycles of attacks have been performed, meaning it is able to use its spiral laser and Nebula Residue Mine attacks during its first attack cycle.
  • Phase 1 laser attacks shoot out 14 spokes of lasers instead of 12.
  • Phase 1 lasers have a larger spread.
  • Phase 1 Slams create rocks upon reaching 90% life instead of 75%.
  • Interstellar Corruption instantly kills the player when inflicted, making Nova Slimers and the bordering arena much deadlier.


  • Spiral clusters of Metanova Ore will generate in the underground Astral Infection.
  • Nova Slimes will start spawning on the surface Astral Infection.
  • Metanova Slimes will start spawning in the Cavern.
  • The Astrageldon Style menu theme is unlocked.


Nova Slimer

Catalyst/Astrageldon (45)



Flying Enemy

AI TypeNova Slimer AI
Damage120 / 240 / 360
Max Life1200
KB Resist100%


  • While Astrageldon is alive, the following events are disabled:
    • Rain
    • Slime Rain
    • Parties
    • Sandstorms
  • The lock on spawning Astrageldon is indicated by a status message, meaning that dying to the Moon Lord will not cause the boss to become locked off.
    • This means that the player can clear the Lunar Events then die to the Moon Lord if they wish to fight the boss without any pillars active.


General resistances

Astrageldon has a damage reduction value of 10%, which increases to 60% during its spiral laser attack. In addition to this, it also has resistance to certain damage types. These resistances go as follows:

  • During spiral laser, star barrage, and Nebula Residue Mine attacks, Astrageldon gains the following resistances:
    • 90% from melee projectiles.
    • 65% damage from stealth strikes.
    • 55% damage from magic projectiles.
    • 75% damage from all other projectiles.
  • At all times, Astrageldon takes 80% damage from true melee damage.

Specific weapon resistances

Astrageldon has specialized damage resistance values for certain weapons, these stack on top of any general class resistances. These resistances go as follows:

  • 90% damage from Leonid Progenitor’s small comets and stars, Luminous Striker, and Vortexpopper when using Hyperius Bullets.
  • 85% damage from The Swarmer.
  • 80% damage from Fantasy Talisman’s stealth strike, Hive Pod’s Hivelings, Leonid Progenitor’s large comets and main projectile, Regulus Riot’s stealth strike, Subduction Slicer’s stealth fire pillars, and Vortexpopper when using Bubonic Rounds.
  • 75% damage from Nebula Arcanum.
  • 70% damage from Malachite’s stealth strike.
  • 40% damage from Duke’s Decapitator.
  • 20% damage from Duststorm in a Bottle’s stealth strike clouds, Wither Blossoms Staff’s primary bolts, and Spikecrag Staff’s spikes.
  • 15% damage from Shard of Antumbra’s stealth strike.


For more elaborate strategies on defeating Astrageldon, including Weapon and arena recommendations, see Guide:Astrageldon strategies.

  • Due to the use of Interstellar Corruption in the fight, the Rod of Discord should not be relied on as the debuff will instantly kill players inflicted by it, unless the player can avoid the Nova Slimers and the bordering arena.
  • The Astral Communicator becomes unusable after defeating the Moon Lord, meaning players shouldn't wait to fight the boss with stronger gear as it will become inaccessible.
  • Running away from the waves of Nova Slimes is more advisable than attempting to kill all of them as they can become overwhelming to try and focus on killing while also avoiding the boss.
  • Baiting Astrageldon into dashing across the border of the arena then flying to the opposite side during its grid mine attack can be a useful alternate strategy as it leaves most of the mines unable to hit the player, though this method is not reliable and the player should be prepared to wedge into a safe spot if an unlucky pattern occurs.


  • The Bestiary entry for Astrageldon: An interdimensional slime with the power of a god. Astrageldon is the paragon of the Astral Blight, and in its quest for mass absorbed its entire universe.
  • The Bestiary entry for Nova Slimer: A highly dense orb of astral gel bearing blades durable and sharp enough to split dimensions. When they are launched at high speeds, they tear holes in the fabric of reality.
  • Astrageldon's first phase's theme is Cosmic Disgust, which was composed by the artist DM DOKURO.
    • Astrageldon's second phase's theme is Galactic Destruction, which is composed by the artist Heart Plus Up!.
      • Galactic Destruction contains motifs from Cosmic Disgust, Heaven's Hell-Sent Abomination, Return to Slime, and the "intimidation" motif used in several post-Moon Lord boss themes.
  • Astrageldon is based on the deprecated Astrageldon Slime boss from Calamity, which has been replaced by Astrum Aureus.
    • "Slime" was dropped from Astrageldon's name due to it being deemed redundant with the inclusion of gel in the boss's name, along with making its name feel weaker.
    • Catalyst's Astrageldon becoming unfightable after defeating the Moon Lord counters how Calamity's Astrageldon Slime gained a massive buff and new drops after defeating the Moon Lord.
  • Astrageldon’s Blighted Asteroid attack is a reference to a similar attack used by Asriel Dreemurr from the game, ‘’Undertale’’.
  • The halo Astrageldon gets in phase 2 is a reference to Astrum Limus from the discontinued Emphatic Untamed Calamity mod.
  • The meteor that spawns when attempting to heal with the Nurse is a reference to a similar mechanic that was previously used in Revengeance Mode, where talking to the Nurse would spawn one of The Leviathan's meteors.
  • The laser projectiles in phase 1 use the same sprite as the Abandoned Slime Staff minion's lasers.
  • All of the boss's For The Worthy seed changes were previously used in Malice Mode.
  • If the Boss Checklist Mod is installed, its unique despawn message will be "The multiversal terror returns to its consumption."


In a universe where Astrum Deus had defeated the tyrannical Devourer of Gods, a new form of the Astral Infection had formed known as the Astral Blight. In this universe, many creatures adapted or transformed quickly to survive in the dangerous lands of the Blight. One creature was, of course, slimes. Slimes are known for being the most adaptable species in existence due to their innate ability to gain the powers of whatever they consume and transform accordingly. Astrageldon is one of these Blighted slimes, but unlike the others it became large enough to consume a black hole within its massive body, which fueled its hunger endlessly. After consuming the entire universe, Astrageldon gained sentience and a godly amount of power. It then continued into our universe to continue its consumption. What Astrageldon was not aware of is that if a black hole continues to consume more and more matter, it will eventually die and release all the energy left over from its existence. Astrageldon, as all things do, will eventually meet its end.

V • D • E • P

Characters: Enemies:

  • Pre-Hardmode
  • Hardmode
  • Superbosses

Pre-Hardmode Enemies


  • Wulfrum Slime


  • Wulfrum Mine

Hardmode Enemies

Astral Infection

  • Ascended Astral Slime
  • Nova Slime


  • Metanova Slime



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