This hidden island in Diablo 4 has a Mythic Fish you can only catch there
Leave the Secret Cow Level the right way, and you can reach a very strange fishing spot.
The secrets just keep coming! Even if this one was already available last season, with all the things hiding around the Secret Cow Level in Diablo 4 Season 15, it is good to give you a reminder that it exists as well. This one is particularly useful if you are trying to collect all of the Mythic Fish.
After leaving the Secret Cow Level, you can end up on a tiny hidden island with a rather unfortunate whimsy skeleton. And yes, you can fish from it. More importantly, this is where you can catch the Vivid Whimsy, a Mythic Fish that appears to be linked specifically to this unusual fishing spot.
How to Reach the Hidden Island
First, you will need access to the Secret Cow Level. So, as usual, either you go through the entire quest, or you find someone who can Moo at you. The second one does make things way easier. Trust me, you do not really want to farm over 1000 cows for 6h straight....
Anyway, once you are inside, clear the area and defeat the Cow King. Since you are here, might as well get his loot. Next is the important part because you do not want to teleport back to town when you are done. Instead, use the Leave Dungeon option. This will not put you back at the entrance, but it will send you to a tiny hidden island somewhere out in the water.
And there is something very strange waiting for you there.
Whimsyshire Lost a Horse, or Unicorn... Something
On the island, you will find the remains of a very... whimsical... animal partially lying in the water. You can interact with the skeleton to get a small piece of lore, but let's be honest, it is pretty clear it escaped from Whimsyshire before eventually ending up stranded here. It did not exactly have a happy ending, but the skeleton is also an important part of this secret because you can fish directly on it. Place yourself on the cliff on top, and cast your line onto the dead body.
This is pretty much the only spot where you can catch the Vivid Whimsy Mythic fish. The island has a small dock where you can fish normally, and you will get a selection of regular fish and some items related to the Bovine cosmetic. But Vivid Whimsy does not appear to come from the normal dock fishing spot. To catch it, you need to fish specifically in the water around the whimsy skeleton.
If you are trying to complete your Mythic Fish collection, you will have to find a way to come here. So if you have already spent hours fishing around Sanctuary and still have not found this one, the Secret Cow Level might be the place you need to visit.
Outside of that, there is not much on the island. You can also find the entrance to the Forlorn Cellar here. However, what you find inside depends on how you accessed the Secret Cow Level. If you have properly unlocked the Cow Level yourself, there are additional things to discover inside the cellar. If you only reached the area because another player mooed at you and gave you access, there is unfortunately not much waiting for you inside.
But you also do not need any of that if all you want is the fish. Just get to the island, find the rainbow skeleton, and start fishing. And yes, this means you can go from fighting the Cow King to catching a Mythic Fish in one very weird trip.