Calamity Mod Wiki
Ark of the Cosmos
  • Ark of the Cosmos.png
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Damage140 Melee
Knockback9.5 (Extremely Strong)
Critical chance19%
Use time14 Very Fast
TooltipFires different homing projectiles based on what biome you're in
Upon hitting an enemy you are granted a buff based on what biome you're in
Projectiles also change based on moon events
RarityRarity Level: 15
Sell 50 Gold Coin.png
Projectiles created
Eon Beam (All)
Eon Beams
Galaxian Star
Galaxian Star

The Ark of the Cosmos being used against a Target Dummy and a more distant Super Dummy.

The Ark of the Cosmos is a craftable post-Moon Lord broadsword that autoswings. It is the final upgrade of the Ark of the Ancients and Biome Blade. It fires an Eon Beam of random colors when swung, including pink, green, blue, and orange. These beams can pierce twice and ignore tiles, inflicting the Elemental Mix debuff on hit. Each beam color also has varying immunity frames on hit, with pink at a highest value of 6 and decreasing in the mentioned order to orange's value of 3.

A column of four Galaxian Stars are also fired inaccurately towards the cursor, which are capable of piercing once, ignoring tiles, and strongly homing into enemies. On hit, stars spawn an additional projectile depending on the biome the player is in. Certain biomes will also debuff the target for 20 seconds alongside spawning a projectile.

Upon hitting any enemy with the blade itself or any of the homing stars, the player will be given a certain buff depending on biomes. Additionally, the player will gain additional buffs along with the biome effects during certain moon events. Both of the buffs provided last 10 seconds.

Its best modifier is Legendary.

Buffs and Effects[]

Moon Event Player Buff
Blood MoonBlood Moon BattleBattle
Frost MoonFrost Moon Rapid HealingRapid Healing
Pumpkin MoonPumpkin Moon Well FedWell Fed

Only one biome effect can be applied at a time. The following is a list of biome effects from highest to lowest priority.

Biome / Event Enemy Debuff Player Buff Projectile Spawned
Astral InfectionAstral Infection Astral Infection (debuff)Astral Infection Gravity NormalizerGravity Normalizer Astral StarAstral Star
JungleJungle PlaguePlague ThornsThorns Crystal Leaf (projectile)Crystal Leaf
Snow biomeSnow / Ice Glacial StateGlacial State WarmthWarmth Ice BoltIce Bolt
Sulphurous SeaSulphurous Sea
Crush DepthCrush Depth WetWet Flairon BubbleFlairon Bubble
The CorruptionThe Corruption n/a WrathWrath Cursed Flame (projectile)Cursed Flame
The CrimsonThe Crimson n/a RageRage Golden Shower (projectile)Golden Shower
DungeonDungeon FrostburnFrostburn DangersenseDangersense Water Bolt (projectile)Water Bolt
DesertDesert Holy FlamesHoly Flames EnduranceEndurance Onyx Blaster (projectile)Onyx Blast
Glowing Mushroom biomeGlowing Mushroom Temporal SadnessTemporal Sadness SpelunkerSpelunker Glowing MushroomGlowing Mushroom
The UnderworldThe Underworld Brimstone FlamesBrimstone Flames InfernoInferno Ball of FireBall of Fire
The HallowThe Hallow Holy FlamesHoly Flames HeartreachHeartreach Rainbow ExplosionRainbow Explosion
Nebula PillarNebula Pillar n/a Magic PowerMagic Power Nebula BlastNebula Blast
Stardust PillarStardust Pillar n/a Summoning (buff)Summoning Stardust Cell ShotStardust Cell Shot
Solar PillarSolar Pillar n/a TitanTitan Solar ExplosionSolar Explosion
Vortex PillarVortex Pillar n/a Ammo ReservationAmmo Reservation Vortex RocketVortex Rocket
None of the above Armor CrunchArmor Crunch Dryad's BlessingDryad's Blessing Terrarian ProjectileTerrarian Orb


For a full crafting tree, see here.


Crafting Station
Cosmic AnvilCosmic Anvil
Ark of the ElementsArk of the Elements1
Auric BarAuric Bar5
Ark of the CosmosArk of the Cosmos1


  • If the player travels into a different biome after a projectile is fired, the projectile's effect will change to the new biome.
  • The Ocean and Underworld biomes are determined by the player's position and depth.
    • Biomes such as the Abyss or the Brimstone Crag will not count as the Ocean or Underworld respectively if they do not meet the position requirements.
      • As most of the Abyss takes place below the Surface layer, it often counts as none of the biomes.
  • Certain projectiles fired from Galaxian Stars are modified:
    • All projectiles fired will have the melee damage type.
    • Rainbow Explosion and Vortex Rocket's immunity frames are modified to use usesLocalNPCImmunity with a hit cooldown value of -1.
    • Cursed Flame, Golden Shower, Water Bolt, Stardust Cell Shot, and Terrarian Orb have their pierce reduced to none.


  • Ark of the Cosmos is useful against enemies who have high mobility or keep a safe distance away from the player as it shoots lots of high-damage, homing projectiles.