The Weight of Chains is a Favor (Side Quest) for Mimir in God of War Ragnarok. This walkthrough will guide you through all objectives of The Weight of Chains Side Quest. For an overview of all quests in the game see God of War Ragnarok All Favors.
Requirement: Access to Svartalfheim
Reward: 1000 Kratos XP, 250 Atreus XP, Making Amends 
Objectives:
- Find the key on the island
- Bring the key to the watchtower
- Return to the creature
- Free the Lyngbakr
- Boat to the Lyngbakr’s eye
Starting Location: The Weight of Chains
The Weight of Chains is automatically started upon arriving at Lyngbakr Island in the middle of the Bay of Bounty in Svartalfheim.
Find the key on the island
Destroy the rocks by throwing you axe at the fire vessel, then head up the ramp and destroy the Wretch Nest. Continue forward to another fire vessel you can destroy, then shimmy along the wall.
Destroy another nest, then lower the elevator and throw your axe at the gear to freeze it. Climb around the wall to the elevator and retrieve your axe to ascend. Jump down to the floor to break it.
Defeat the Bergsra Mother, then open the chest for the key.
Bring the key to the watchtower
Head to the watchtower on the island to the south. Climb the wall and use the key on the door, then interact with the gong.
Return to the creature
Head back north to Lyngbakr Island.
Free the Lyngbakr
Climb the chains and deal with the Draugrs. Destroy the fire vessel to open the path and break the binding, then throw your axe at the chain.
Continue along the new path that appears. Deal with the enemies and climb the chain to find a lore marker to the right. Interact with it then turn around and climb up the wall.
Jump across the gap to find an artefact on the ground.
Return back down the wall and swing across to the next area. Continue forward until you can descend a chain to find the next binding. Break it and free the fin. Destroy the nest that appears, then use the fire bombs to clear the rocks on the dock down below near the tail.
Before you return to the boat, grab another fire bomb and go up the first path you opened and destroy the rocks there. then swing across and crawl through the hole to find an Odin’s Raven.
Return to the boat and head around to the dock you opened up. Deal with the waves of enemies, then break the final binding. Slide down the rope, open the legendary chest, then break the chains on the tail.
Boat to the Lyngbakr’s eye
Break open the gate and return to the boat, then head over to the Lyngbakr’s eye.
This finishes The Weight of Chains Side Quest in God of War Ragnarok.
For all other quests refer to God of War Ragnarok Walkthrough.
Did all of the above but the trophy never popped.