On this page of the Assassin's Creed Valhalla guide, you will find a detailed walkthrough description of the mission Going Deeper.
After explaining a series of dreams about Asgard, it's time to delve into another one and head to Jotunheim.
The reward for completing the mission: an opportunity to travel to Jotunheim.
Collect the plants for Valka's next potion
Head to the Centu area and enter the hidden cave at the location indicated in the image above. The entrance is located in the cottage.
The doors to the rest of the underground complex are closed. The key you need hangs from a chain. You can get it by jumping over the chasm.
As you jump between obstacles, go through the cave and collect the distinctively marked story items. You do not need to search for the keys to complete this task - they are associated with Wealth.
Bring the plants for Valka
Once you have collected the necessary ingredients, return to Ravensthorpe and bring them to Valka. The woman will prepare a decoction that will allow you to travel to Jotunheim. Drink the beverage to complete the quest.