The Destroyer can be summoned manually using a Mechanical Worm at night (7:30 PM to 4:30 AM). It also has a 1/10 (10%) chance to spawn naturally at dusk once a Demon or Crimson Altar has been destroyed, as long as it has not yet been defeated at least once in the current world.

Where do you spawn the mechanical worm Terraria?

The Mechanical Worm is a consumable item that summons the Destroyer. It can be obtained by killing any hard-mode monsters as long as the Destroyer hasn't been defeated in that world. The Item can be used to summon the Destroyer on Hard-mode and Pre-Hardmode Worlds but must be used at night or it will not work.

When can I summon a mechanical worm?

The Mechanical Worm is a consumable item that summons The Destroyer. It can only be obtained by a first-time player once Hard Mode has been activated. If it is not a first-time player, it can be used to summon The Destroyer anywhere in both pre-Hard Mode and Hard Mode worlds but must be used at night.