Clear Mörkhalla and halt the Jotun invasion

1. Mark the Mörkhalla structure and establish a small exterior recovery cache before carrying the key inside.
2. Reach the upper access. Postmode and redfreshet describe Grappling Hook access; a catapult is reported by Postmode only and is not a required method here.
3. Descend to the chained door and verify that it requests the Intricate Key. The build contains two differently configured Mörkhalla gates under the same English display name; one consumes the key and cannot close, while the other does not consume it and can close. Until the player-visible checkpoint is mapped by reproducible observation, do not promise that this key survives or is refunded.
4. Confirm a retreat path immediately after the door opens before beginning the full descent.

Mechanics sources: SteamDB: Valheim 1.0 patch notes (build 25185596)Local vanilla extraction: Deep North build 25185596Postmode: completed Deep North walkthroughredfreshet: Mörkhalla guide

1. Work down floor by floor, clearing enemies before using corner stairs or dropping into the next space. Keep the path behind you recognizable.
2. At the bottom, find the Malicious Ice and destroy its central portion. Current walkthroughs report an on-screen Jotun advance message.
3. Leave the dungeon, reach safety and open the world map. Look for the marked Jotun Invasion instead of continuing to search Mörkhalla for the Blood.
4. If no marker appears, return to the bottom only after repair and verify that the central ice core was fully destroyed. The sources do not establish a reset timer or a command-free repair for a missing event.

Mechanics sources: Postmode: completed Deep North walkthroughredfreshet: Mörkhalla guide

1. Plan a route to the flashing invasion marker. The event can pull the Deep North route back across earlier biomes, so restock at home rather than leaving straight from the dungeon while depleted.
2. Enter the marked area, clear the invading enemies and work toward its central Malicious Ice.
3. Destroy the central ice and collect Malicious Blood. Store it before starting another key cycle.
4. Repeat the researched dungeon-to-event loop until you have three Blood. The build-verified Kall altar count is three. Prepare another complete key for another locked Mörkhalla; the two gate defaults do not prove that the key used at your checkpoint is reusable.

Mechanics sources: Local vanilla extraction: Deep North build 25185596PC Gamer: Valheim 1.0 progression guidePostmode: completed Deep North walkthroughredfreshet: Mörkhalla guideValheim.tools: Kall Fimbulbringer