Is a side quest in Novigrad with suggested level 14.

Head to the designated map marker, and you'll meet a halfling family, and their bees are being terrorized by what they believe is an Apiarian Phantom.

After talking to the halflings, follow one of them to where the initial frozen over bee hive was found.

Examine the bee hive, and then use your witcher senses to find the tracks of the monster that attacked it. The tracks lead to the river, so swim over the river and find the tracks again. You will encounter some Drowners on the other side of the river.

You'll eventually discover the tracks again. Keep following the tracks and you'll find a halfling house that wasn't completed, with a locked basement. As you try to open the door, one of the halflings arrives, and gives you the key.

Use this key, and open the door. As you enter the monster turns out to be a Hound of the Wild Hunt. It runs outside. Get on your horse and chase after it, and swing at it with your sword. It will then stop running, and want to fight.

After defeating the Apiarian Phantom. Loot it and return to the halfling family to receive your reward.