People all over the world are scratching their heads wondering where the yellow longship is in Assassin's Creed Valhalla. It plays an important part in the events that lead up to The Stench of Treachery, a quest that tasks you with deciding which of Soma's three inner circle advisors you think has betrayed her. If you want to know who the traitor is, the guide linked in the previous sentence has all of the details you need — however, if you want to find out for yourself and are just stumped in terms of where the yellow longship is, stay right here.
The yellow longship is significant because it gives you a pretty concrete idea of who the traitor is. After finishing Glory Regained, Soma reveals that pushing Wigmund out of Grantebridge isn't the only problem on her plate. Remember she mentioned that it seemed as if the invaders came out of nowhere? As it turns out, one of her three closest advisors collaborated with Wigmund to coordinate an attack through a secret escape tunnel Soma had built.
After speaking to Soma, you can go down into the tunnel yourself — the entrance is accessible via a trapdoor in Soma's longhouse. After making your way through the whole tunnel, you'll notice that there's a yellow cross painted on a rock by the exit. You can use Odin's sight to follow a trail of paint that dripped on the ground as Wigmund escaped. It's very similar to how you might use Geralt's Witcher senses in The Witcher 3.
Eventually, the trail of paint will lead you to a small pier. Sure enough, there's an empty bucket of paint right next to the water. Eivor is able to imagine a flashback sequence where a hypothetical escape was made, and deduces that this paint was used to paint a longship for Wigmund to escape on — this is obviously the yellow longship you're looking for.
The yellow longship isn't necessarily very easy to find, primarily because it's pretty far away. The best way to find it quickly is to use Raven's sight — don't bother trying to find it while Eivor is on the ground. If you fly approximately 700 metres northeast from your current location on the pier, you should be able to see a longship docked at an island with a very poor yellow paintjob. It's basically just a couple of yellow lines scrawled across the side, to the extent that it wouldn't really fool anyone into thinking that the ship hadn't been stolen in the first place.
While you're still in Raven's sight, place a custom marker on the area beside the yellow longship. Once you've done that, use your warhorn to call your ship. If you put the ship into auto-sail mode, you'll arrive at the yellow longship in no time, and will be able to piece together who Soma's traitor is all by yourself — after some fighting.
For more guides, check out our complete Assassin's Creed Valhalla walkthrough.