Dusky Thread is a non-consumable tool item in Fisch that functions as the first required piece for crafting the Astraeus Serenade. You don’t buy it, you don’t trade for it, and you don’t get it from random drops. You earn it by completing Merlin’s Astraeus Serenade quest part 1.
Dusky Thread requirements (Astraeus Serenade quest part 1)
Merlin’s first Astraeus Serenade hand-in asks for the same fish three times, but each one must have a different mutation applied. The three turn-ins are:
- Celestial Radiant Crystal
- Serene Radiant Crystal
- Breezed Radiant Crystal
You’ll need to have Merlin’s earlier quests finished before Astraeus Serenade becomes available.
Where to find Radiant Crystal (Mineshaft access)
All three Radiant Crystals are fished from the Mineshaft, a location tied to the Merlin rework. Getting there starts behind Merlin’s house, where you jump into the sea to access the Chasm route that leads to the Mineshaft.
Entry is gated by Merlin’s Veil. Without it, you can’t access the area normally, so the practical first checkpoint is making sure you’ve progressed far enough with Merlin to have the Veil requirement handled.
How to get Celestial Radiant Crystal
Celestial mutation: this one is locked to the Celestial Rod. During the Celestial Bonus admin weather event, Celestial mutation has a 100 percent chance to apply, which turns a Radiant Crystal catch into a Celestial Radiant Crystal.
How to get Serene Radiant Crystal
Serene mutation: the cleanest path is the Polaris Serenade Rod, which has a 20 percent chance to roll Serene. There’s also the Duskwire Rod, but its odds are much lower: 2 percent normally, or 4 percent after a perfect catch.
Both Polaris Serenade Rod and Duskwire Rod are obtained from the Underground Music venue.
How to get Breezed Radiant Crystal
Breezed mutation: the Wind Elemental Rod is the relevant tool here, with a 25 percent chance to roll Breezed on catches, letting you land a Breezed Radiant Crystal from the Mineshaft.
Turning in the fish to Merlin (and what you receive)
Step 1: Talk to Merlin to start Astraeus Serenade quest part 1 (this takes place on Sunstone Island) and confirm the three required mutated Radiant Crystals.
Step 2: Fish in the Mineshaft until you have all three variants: Celestial Radiant Crystal, Serene Radiant Crystal, and Breezed Radiant Crystal.
Step 3: Return to Merlin and submit the three fish. Dusky Thread is awarded as the quest reward and appears in your inventory.
How Dusky Thread is used
Dusky Thread is a crafting material tied to the Astraeus Serenade Rod. Once you’ve collected the full set of required ingredients, you can craft the rod, with Dusky Thread serving as one of those components.
If you’re trying to shortcut the process through trading, it won’t work. Dusky Thread is earned through this quest chain.
