Dreadnautilus

The Dreadnautilus is a Hardmode enemy summoned by Fishing during a Blood Moon. It is one of the five enemies that can be summoned by fishing during a Blood Moon during Hardmode, the others including the Wandering Eye Fish, the Zombie Merman, and two other Hardmode-exclusives, the Blood Eel and the Hemogoblin Shark. The Dreadnautilus is rarer than the other four Blood Moon fishing enemies, occurring only 1 in 10 spawn attempts on average, and is considered the most difficult to battle.

Attacks

 * Spins around the player for roughly 3 seconds. It will damage the player upon contact.
 * While this attack is charging, Dreadnautilus will face away from the player and will reflect projectiles.
 * Fires a rapid spray of red projectiles at the player. During this attack, the Dreadnautilus will turn invincible.
 * Briefly glows crimson and summons three red symbols. After a moment, each symbol will summon a Blood Squid, which will attack the player with a ranged projectile.

Tips

 * Summon weapons are useful for handling the Blood Squids while the player focuses on the Dreadnautilus.
 * Using the Chum Caster gives the player a greater chance of finding the Dreadnautilus and other blood moon fishing enemies. This combined with Chum Bucket s will give the player the best chance to hook a Dreadnautilus. Using Sonar Potions will allow you to skip past other blood moon fishing enemies, letting you fight the Dreadnautilus more over the course of the night.
 * Of the 3 attacks that the Dreadnautilus employs, only the Spin attack will phase through walls, since the enemy itself also phases through walls. A good strategy to cheese the enemy is to build a box and use weapons that can attack through the walls. When you see the enemy charge up for the spin attack, temporarily leave the box and re-enter after the enemy is finished.
 * Since this fight takes place at night with a possibility of rain, visibility can be an issue and can make projectiles difficult to perceive. Using a Hunt er potion, along with a Night Owl potion and Shine potion, will help with visibility.

Trivia

 * Similar to the Sand Elemental and the Ice Golem, the Dreadnautilus is not a boss or mini-boss even though it has stats comparable to a boss. This is evidenced by its lack of a health bar and the fact that it drops a banner, not a trophy.
 * It resembles a, the creature after which it was named.
 * Its name is a portmanteau of "," a type of early 20th-century battleship, and "," a marine mollusk of the Nautilidae family.
 * Its original name was "Blood Nautilus" in an official trailer.