The Calamitas Clone does not spawn on her own and requires the player to summon her with the Eye of Desolation during the Night.

Calamitas Clone is a Hardmode boss that is usually fought at the same tier as Plantera, after all Mechanical Bosses have been defeated. Calamitas Clone can be spawned by using an Eye of Desolation on the Surface at night.

It can be summoned by using a Decapodita Sprout while in the Glowing Mushroom biome. While it spawns initially passive, it begins to attack once damaged, jumping and lunging at the player. It fires bursts of mushroom projectiles and summons many Crab Shrooms and walls of mushrooms, which float down in the players direction, as it takes damage.

Aquatic Scourge: Natural spawn or by using Seafood Brimstone Elemental: Use Charred Idol in the Brimstone Crag Calamitas Clone: Use Eye of Desolation at night

The Eye of Desolation is a craftable Hardmode boss - summoning item that is used to summon the Calamitas Clone. It can be used anywhere during the night.