The One and Only, Diederik is the third and final mission in the Lake Stoneback Crab side quest chain in Crimson Desert. After Diederik gets flung off the Queen Stoneback Crab during the previous fight, you need to track him down and check whether he survived the launch.
Where this mission sits in the questline
The Lake Stoneback Crab quest is a three-part chain that starts with a group of merchants and ends with a brief reunion. Each step depends on the previous one being cleared, so you cannot trigger the Diederik check-in until the Queen Stoneback Crab fight is over.
| Order | Mission | Focus |
|---|---|---|
| 1 | The Wolf's Ballad | Meet the Redfox Merchants and start the chain |
| 2 | The Queen's Lake | Confront the Queen Stoneback Crab |
| 3 | The One and Only, Diederik | Find Diederik and confirm he's unhurt |
How to complete The One and Only, Diederik
The mission itself is short. Diederik gets thrown clear of the Queen Stoneback Crab during the boss encounter, and the objective marker updates to his landing spot once that fight ends. Your only task is to reach him and start the dialogue.
Step 1: Finish The Queen's Lake by defeating or driving off the Queen Stoneback Crab. Diederik's location only updates after that fight resolves.
Step 2: Follow the quest marker to where Diederik landed near the lake. Approach him to trigger the inspection prompt.
Step 3: Speak with Diederik. Despite the impact, he doesn't have a single scratch on him, and the mission completes the moment the conversation ends.
Rewards for finishing the quest
Wrapping up the Diederik check-in closes out the entire Lake Stoneback Crab questline, and the payout reflects that. You walk away with a movement upgrade and a stack of gemstones useful for crafting and trading.
| Reward | Type |
|---|---|
| A.T.A.G. Thrusterpack Mk II | Equipment |
| Diamond | Gemstone |
| Garnet | Gemstone |
| Azurite | Gemstone |
| Epidote | Gemstone |
The A.T.A.G. Thrusterpack Mk II is the standout item here. It's a traversal upgrade tied to the Delesyia tech line, and getting one through a side quest saves you the trouble of grinding for it elsewhere. The four gemstones (Diamond, Garnet, Azurite, and Epidote) are valuable for accessory crafting and selling.
How to confirm the quest finished
You'll know the mission registered when the on-screen quest log clears the Lake Stoneback Crab entry and the rewards drop into your inventory. Diederik's completion text reads that he looks perfectly fine, "without so much as a scratch," which is the cue that the chain is fully closed.
If the quest doesn't advance after talking to him, make sure The Queen's Lake mission is actually completed, and you didn't leave the area mid-cutscene. Reloading the zone usually pushes the marker to update.
Why this mission exists
The Lake Stoneback Crab chain is one of the lighter side stories in Crimson Desert, built around the Redfox Merchants and their oddly indestructible companion. Diederik surviving the boss fight unharmed is the punchline of the whole arc, which is why the final mission is just a quick conversation rather than another encounter. Treat it as a payoff, grab the Thrusterpack, and move on.