Fossegrim lives in the icy cave next to the Mountain Plateau. He told you about the way to make water dance.
What do I need to do?
I have all of them
You have to:
The stream that goes under Trollhilde's bridge.
There's that tainted pond in the Poisoned Forest.
This refers to the pond that is in the cave right of Nokken's pond.
The Yule Cat has some meat baking.
Three charged stones, the flute and the meat from the Yule Cat? Nice. Take them to Fossegrim. He will teach you how to make the water dance.