DREDGE

Story-Related, Cannot be missed

Stellar Basin is the intended location for the third Relic you will retrieve. When you arrive at the Basin you will find an abandoned Research Outpost and a large basin of deep ocean that is lorded over by a giant tentacled creature. You will be unable to traverse the center area of the basin and you will find that many of the fauna in the Basin and surrounding areas are only caught with Abyssal and Hadal rods. All of these issues will be resolved through a few Pursuits and you will be able to get the Ring relic well before you finish some of the tasks in Stellar Basin if you choose to take the quickest way.

Head northwest of the four crescent land masses that surround the Basin to find the Old Fortress. Within the Old Fortress is the Researcher. She will enlist you to gather three specimens so she can complete her research to get the Abyssal rod prototype you will need.  She needs one of each of the following fauna:

The important thing to know about this Pursuit is that the Aurora Jellyfish can ONLY be caught with a Trawl Net. If you have not already made two changes to your boat, you will need to do so before you can complete this Pursuit. To fit your boat up with a Trawl Net you will need to first upgrade 4 of your Rod spaces to also support a Trawl Net by going into the Dry Dock in Greater Marrow or any of the four Floating Docks operated by the Traveling Merchant, depositing two cloth, one lumber and $125. This will allow the four squares on the left side of your cargo hull to be used for rods or trawl nets interchangeably.  Next, you simply need to buy and install any net (The first one will be available directly after making this upgrade and costs $250. Don't worry about the price, because using a net adds a useful amount of passive income while you are moving about the map. Trawl Nets just need repairs every now and again, but fish stay fresh in the submerged net and there is a lot of space to fill without any labor on your part..

Once you can patrol the rim of the basin for the three specimens, you should head out at night and gather one of each of the three requested fauna and return to the Researcher. She will then instruct you to find the Prototype Parts at the Research Outpost. There you will find the Prototype, as well as two research parts. There is also an additional research part just to the right of the Outpost behind the rock. You will need one part for the next step, but you may as well grab them all.

On your next visit to the Researcher, the prototype will be handed back to you as a rudimentary Abyssal Rod. The Researcher will also give you a Repulsion Machine, which once hooked up to the Generator at the Research Outpost will repel the Kraken into hiding to give you time to fish the center of the Basin. 

The Researcher will task you with collecting four more specimen and the Relic will be up for grabs now that you can access the middle of the Basin. Before you activate the Repulsion Machine, you should use one of your research parts to upgrade the Prototype Abyssal Rod to the Bottomless Lines Abyssal/Hadal Rod that will allow you to catch everything you need to complete this area. The rod costs $450 and takes up a 2X3 "L" shape so you will need to upgrade your rod spaces to accommodate such a space if you haven't already (One Metal Scrap, One Cloth, Two Lumber and $95)

Once you have the Abyssal/Hadal Rod and the Generator is rigged with the Repulsion Machine, activate it and start gathering. You will have a decent amount of time to gather the four specimens in the Basin, as well as the Ring Relic and even the first Recording Rarities Exotic fish that is right at the mouth of the deep basin area. Each of the items you can catch will take up a good deal of space so don't worry about getting all of them on your first run, you can always reactivate the Repulsion machine as many times as you need.

The Items to grab in the Basin are:

Give the specimens to the Researcher and once she has all four, the Pursuit will be complete. Your reward is a book that gives you a 15% chance not to reduce fish stocks when catching with a rod. it isn't much, but it helps.

The Gulper Eel can be reported to the Traveling Merchant (See Providence ) and then sold. If this is the third relic you are turning in, then The Ring can be taken back to The Collector to receive the Banish ability (which scares away almost all Panic hallucinations and beasts for a time period) and this trophy.

Retrieval of the relic and all Stellar Basin Pursuits for the Providence  trophy can be found in the video below. Please take note that the information in the below video was made before Patch 1.1.0 was released. The timer has now been removed from the Hooded Figure Pursuits, so you should have an easier time succeeding on that Pursuit: As stated above, the Loosejaw was supposed to be found inside the basin for the Research Assistant Pursuit after Patch 1.1.0, but is still just outside the circle of islands so the information regarding its location and how to catch it in the video remIans correct: