Dreadnautilus

The Dreadnautilus is a Hardmode enemy summoned by fishing during a Blood Moon. It is one of five enemies that can be summoned by fishing during a Blood Moon in Hardmode, the others being the Wandering Eye Fish and Zombie Merman (which are also available in pre-Hardmode), and the Blood Eel and Hemogoblin Shark. The Dreadnautilus is rarer than the other four Blood Moon fishing enemies, spawning from only of spawn attempts, on average. It is widely considered the most difficult of these five enemies. If the Dreadnautilus is not defeated by dawn (4:30AM), it will fly away and despawn.

Attacks

 * It charges at the player for roughly 3 seconds, normally spinning around them. It will damage the player upon contact.
 * While this attack is charging, the Dreadnautilus will face away from the player and will charge up for about 3 seconds before performing the dash.
 * It fires a rapid spray of red projectiles at the player and recoils after each burst. It reflects all projectiles during this time. It can reflect bullets, arrows, and darts, but not rockets, and the projectiles of numerous other weapons. For the complete list, see List of reflected projectiles.
 * It briefly glows crimson and summons three red symbols. After one and a half seconds, a Blood Squid will emerge from each symbol, and the symbols will despawn again after another one and a half seconds. The Dreadnautilus will only perform this attack if the player is less than 125 tiles away and there are fewer than three Blood Squids currently alive. Symbols can only be summoned in the air, water, or honey, and with an unobstructed line of sight to the player.

Tips

 * The Sonar Potion will detect if the Dreadnautilus is about to be hooked, and can give the player a moment of warning to back away and activate their potions.
 * Using the Chum Caster gives the player a greater chance of finding the Dreadnautilus and other Blood Moon fishing enemies. Using Sonar Potions will allow the player to skip past other Blood Moon fishing enemies and unrelated catches, letting them fight the Dreadnautilus more over the course of the night.
 * Summon weapons are useful for handling the Blood Squids while the player focuses on the Dreadnautilus. The Blade Staff is a great choice due to its defense-ignoring capabilities, and will ignore all of the Dreadnautilus' defense.
 * Inflicting the Ichor debuff, e.g. via the Golden Shower, can be helpful for lowering its high defense.
 * Hiding under blocks is useful as it blocks Blood Squid's projectiles, as well as the red spit projectiles the Dreadnautilus employs.
 * Of the three 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 like the Daedalus Stormbow with Ichor Arrows, or use Summons. The spin attack only hits once per cycle, since the AI defaults to spinning around the player without touching them if they stand still, so the player can tank it by using Campfires, Heart Lanterns and honey (and Regeneration Potions and Well Fed buffs if the player is in higher difficulties).
 * Since this fight takes place at night with a possibility of rain, visibility can be an issue and can make projectiles difficult to perceive as the blood-colored rain is too similar in color. Using a Hunter 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, the fact that it drops a banner instead of a trophy and the fact that it does not drop a Relic in Master Mode.
 * Despite this, it is referred to as a miniboss in the.
 * It resembles a, the creature after which it is 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, as seen in the official Journey's End trailer.
 * Re-Logic may have gotten the idea for adding a shellfish boss to the game from an ' tweet by Cenx, stating that a boss called the Conch of Fish would be added, playing off the acronym WoF for the Wall of Flesh.