The main quest of DREDGE revolves around the collection of five relics. Each relic is at first made inaccessible by a barrier, locked Ability, or danger that the player must first overcome to obtain it. Each relic is marked by a column of red light that stretches into the night sky and has a purplish red background when in the cargo. They cannot be discarded or sold, returning them to the Collector being the only method of getting them out of the Fisherman's cabin or cargo. For each relic returned, the player is rewarded with a new Ability.
Warning: The following article contains large amounts of spoilers.
The following information
contains spoilers regarding the story or ending of the game. Discretion is advised.

Although the Handkerchief isn't counted as a relic on the save screen, the Handkerchief is the first item the player recovers that has a relationship to the Book of the Deep. This can be recognized by the background colour when the item is in the player's cargo. Additionally, the Collector identifies the piece by its crimson colours and silver stitching. Unlike the other relics in game, the Handkerchief is not used in the final ritual.
For returning the handkerchief, the player is rewarded with dredging equipment.
The following information
contains spoilers regarding the story or ending of the game. Discretion is advised.

The Ornate Key is the first relic the Fisherman dredges from the depths.
It is the key which belongs to the Music Box, however, the key has never been used. In the Note "Artifact Manifest", it was left unturned "for fear of damaging the mechanism; pending inspection by locksmith." This also implies that the Key had been separated from the Music Box for quite some time. Later, when the Music Box is returned to the Collector, he neglects to use the Key. Finally, during the ritual, the Collector explicitly inserts the Key yet when he throws in the Music Box, the Key is left unturned.
The Ornate Key is located Southwest of Greater Marrows.
It takes up four slots in an L-shape.
The following information
contains spoilers regarding the story or ending of the game. Discretion is advised.

The Rusted Music Box is the second relic collected by the Fisherman. According to the Note "Artifact Registry", it has the letter J carved in the base, implying that it was previously owned by Julie, the Collector/Fisherman's wife.
The Rusted Music Box is located in Gale Cliffs, locked behind an explodable wall in the bay.
Thus, the Music Box can't be collected until the player unlocks explosives.
It takes up six slots in a 2x3 grid.
The following information
contains spoilers regarding the story or ending of the game. Discretion is advised.

The Jewel Encrusted Band is the third relic the Fisherman collects. It was the engagement ring the Fisherman used to propose to Julie.
The Jewel Encrusted Band is located in the center of the Stellar Basin.
The Ring can't be collected until the player unlocks Hadal fishing and activates the generator at the old research station with the Repulsion Machine attached, or uses the Banish Ability.
It takes up four slots in an 2x2 grid.
The following information
contains spoilers regarding the story or ending of the game. Discretion is advised.

The Shimmering Necklace is the fourth relic the Fisherman collects. It was a gift from the Fisherman to Julie. A receipt recovered as a message in a bottle shows that it was custom engraved to read "For Julie, my shining star."
The Shimmering Necklace is located in the Twisted Strand, swallowed by a Mind Sucker.
The Necklace can't be collected until the player unlocks mangrove fishing, and mixed bait.
It takes up four slots in an 2x2 grid.
The following information
contains spoilers regarding the story or ending of the game. Discretion is advised.

The Antique Pocket Watch is the fifth and final relic the Fisherman collects. It was gifted to Julie in the will of the Fisherman's mother. She accepted it begrudgingly. The keychain attached is likely the keychain Julie kept from the christening ceremony of the boat formerly known as Ocean's Riches. It is theorized that keeping this chain is what brought misfortune upon the couple in finding the casket.
The Antique Pocket Watch is in the possession of the Fanatic, off the shore of the Devil's Spine.
The Pocket Watch can't be collected until the player unlocks volcanic fishing, although this can be bypassed using the Atrophy Ability.
It takes up three spaces in an L shape.
Additional Info
The following information
contains spoilers regarding the story or ending of the game. Discretion is advised.
The relics do not need to be gotten in order and do not correspond to a certain Ability. For example, if you get the Pocket Watch first it will grant you Haste instead of the Key. The abilities are entirely reliant on how many relics you get instead of each one.
The order The Collector Pursuit urges you to go in is as follows: The Key from The Marrows, the Music Box in the Gale Cliffs, the Ring in Stellar Basin, the Necklace in the Twisted Strand and the Pocket Watch in Devil's Spine.
Nothing happens if you collect them out of order.
You awarded the abilities in this order for each relic (minus the Handkerchief, which gives you the ability dredging. First relic gives you Haste, second gives you Manifest, third gives you Banish, forth gives you Atrophy and the fifth gives you the ending (if you choose so).
Trivia
- Unlike other items you can dredge, the relics have a red glow about them, which creates a beacon at night.
Relic locations can be identified by these red wisps.
Red beacons of light show you the locations of the relics in the night.
The following information
contains spoilers regarding the story or ending of the game. Discretion is advised.
- While experiencing maximum Panic, the names and descriptions of the relics change, becoming smaller and more personally named and described, hinting at the Fisherman's familiarity with these items.
- The Handkerchief does not change.
- The Ornate Key, "An abnormally large and heavy key, cast from an unfamiliar metal. The teeth of the key are curved, and sway before your eyes like tendrils." becomes Antique Diary Key, "A small key with ornate loops on the handle. The teeth are simple - whatever lock it opens must be quite crude."
- Rusted Music Box, "A large oak box with a rusted hand crank on the side. It emits a low, rhythmic chime as it rocks with the waves." becomes Music Box, "A delicate music box. The handle spins freely. Inside, she's still humming"
- Jewel Encrusted Band, "A golden band, large enough to fit around a child's waist. All manner of gemstones are affixed to it, seemingly at random." becomes Engagement Ring, "The void creeps into whatever cavities it can.
She said yes."
- Shimmering Necklace, "A large and ornate necklace. Ivory teardrops flank the central setting - an emerald trapped by four cresting waves." becomes Her Chains, "The waves keep her now."
- Antique Pocket Watch, "The clock face swims underneath cracked glass, hands spinning erratically." becomes Her Watch, "The hands are stopped dead, frozen in the moment."