The Power of Nerthus - Act 5 Story Quest
The Power of Nerthus is the 3rd Story Quest of Act 5 and starts by speaking with Teutorigos ~ Prince of Glauberg (pictured above) after completing the previous quest, The Warrior Princess. This quest is quite long with many different steps, the first of which is to travel to Nerthus Sanctuary which is a bit of a run away.
Prior to reaching the Nerthus Sanctuary there will be quite a few Side Quests you pass along the way. Below is a list of all the Side Quests that take place between Glauberg and Nerthus Sanctuary. Of that list I strongly recommend you do not skip The Trapped Nixie as it'll give you 1 Skill Point for completing it.
Note: You will pass through Tuetoburg Forest on your way to Nerthus Sanctuary. This location is one of the best EXP Farming locations in the game.
Side Quests In Area:
The Troubled Son (Glauberg)
Celtic Plaid (Glauberg)
Little Friends (Weser Uplands)
The Trapped Nixie (Wild Heathlands)
The Kornwyf's Scythe (Wild Heathlands)
The Magic Cauldron (Fafnir's Cave has a piece we need)
You'll find the entrance to the Nerthus Sanctuary in the northern portion of the Suebi Lakelands. Our goal inside of the sanctuary is to defeat the 4 Ancients, their locations are all marked on my map below. The fights with them are pretty straight forward, they have very few unique mechanics and serve as mostly mini bosses.
Tip: Return to Teutorigos in Glauberg and speak to him after killing all 4 of the Ancients in the Nerthus Sanctuary. He will give you EXP and Gold as a reward.
Once all 4 Ancients are defeated the energy wall which was previously up in the Inner Sanctum will now be gone and you will be able to pick up the Mistletoe of Nerthus by clicking on the Altar of Nerthus (pictured above). DO NOT FORGET THIS ITEM!!! You will be unable to speak with the King in Scandia unless you have the Mistletoe of Nerthus in your inventory.
Follow the stairs up and out of the Inner Sanctum and you will find yourself on Zealand Coast. Here you will need to collect 3 items for Wodbald in order to sail to Scandia. There is an Embossed Silver Plate (2) piece here for you too which is part of the Magic Cauldron Side Quest in Scandia. I'd recommend getting this now too so you don't have to travel back for it.
Speak with Wobald after you've obtained all 3 of the items you need and he will allow you to sail to Scandia. In the northern portion of King Gylfi's Settlement you will find a guard by the name of Hlif. Speak with her and so long as you have the Mistletoe of Nerthus she will let you through.
Head inside of the King's house and speak with him to complete this quest and begin the next one, Scandia Under Siege.