Custos is the god/spirit of Guardians, Ocean Monuments, and Updates.
Food: Any kind of raw fish.
Weapon: Potion of Mining Fatigue and Sponge
Armor:Reinforced Prismarine Armor
Blocks: Anything under the sea.
Shrine: Make a plus with wet sponge on the ground, then put gold blocks in the corners. Then, put dark prismarine atop the gold, and a sea lantern atop the middle wet sponge.
Custos was created by the other gods, the keep balance and protect the Oceans.
Level 1: Start your journey. Edit
Go to the nearest Deep Ocean, then without using a water breathing potion, go to the nearest Ocean Monument.
Navigate your way threw the temple and do not kill any Guardians, as they are the sacred animals of Custos. Kill all Squids, as the temple must be purified from their inky contamination.
Level 3: Collect your Treasure. Edit
Mine all 8 Gold Blocks in the center then swim to the surface. If you are a true follower of Custos, then you will not have drowned.
Extra Challenge: Collect all sponge as well, as it is evil and must be stopped from drying up Custos.