Weird quest marker in Velen (bug or feature?)

[guardian_of_the_moonserpent]

Soooo I did the short side quest line about the man hauling plague victims through Velen (and later turning out to have caught the plague) to the end, for the first time (killing the infected man by his request and burning the body). Shortly after I found a new quest marker in Velen, SW of Crow's Perch. If you look at the map, there's a small circular pond right at a road there.

I'd write it off as a bug in the game, but weirdly, there's a tiny "island" in the middle of that pond - maybe a meter across or so - with some mushrooms and herbs growing on top of one another, and the marker points me to right there. Weirdly specific thing for a bug.

Is it just a truly weird chance occurance or is that actually some rare quest? *scratches head*

[guardian_of_the_moonserpent]

I should add, I can't interact with that location in any way other than pick the herbs and shrooms, and witcher senses also show me nothing.

[Furiey]

It's a bug, the marker is only supposed to appear if you don't kill him. His ghost will turn up there.

[guardian_of_the_moonserpent]

Merci :)