Health: 400 
Armor: 10 
The Leviathan is a boss that can be found in the Sunken City. To defend against its debuffs, you can eat blessed Amethyst Crab Meat, which is dropped by the Amethyst Crab. It might also be a good idea to use a Trident as your weapon of choice, since the fight will be underwater.
Inside The Sunken City is the Altar of Amethyst. Make sure to search for this before summoning the Leviathan. When you place the Amethyst Crab Meat on the Altar, it will become blessed after a few seconds. Only after being blessed and consumed will it give you immunity to the Leviathans debuffs.
To summon the Leviathan, you must place an Abyssal Sacrifice on the Altar. To craft this Abyssal Sacrifice, you’ll need some vanilla drops as well as drops from mobs and the Coralssus or the Coral Golem.
The Leviathan is a two-phase boss. It enters the second phase after it reaches half-health. The Leviathan will apply multiple debuffs to you, such as the Abyssal Burn, Darkness, and the Abyssal Fear. These debuffs turn your health purple, applying damage over time and preventing HP recovery.
There is a huge variety to the Leviathan’s attacks. You can read more about them on the unofficial wiki.
Upon being slain, the Leviathan drops an Abyssal Egg, which can be hatched into an untamed Baby Leviathan. This Baby Leviathan can then be tamed with Tropical Fish.