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Vigrid is the final area of the game, reachable by traveling east from Asgard. It's usually full of mountains to the west where you'd first arrive. Speed up & save before you teleport to save time(locus mastery is useless here).

The good and evil gods are battling it out when you arrive. Both have ridiculously high HP, so attempting to personally help in the battle won't do. In fact, the evil gods will one-shot you if you step in a space adjacent to them. Teleporting (randomly) is risky, but worth it if you haven't yet burned your potion of second life. If an evil god is in your way, zap him with a wand of displacement (Crazy, right? ;) but it's the only thing you can direct towards them and survive as you won't be in their line of sight when they look at you.)

Your goal is to deliver all your remaining artifacts (Mimming, Mjollnir, Gungnir, and Tyr's arm) within 80 turns. To deliver each item simply stand next to the appropriate friendly god with the item in your pack (not in a red bag).

After everything is delivered, simply wait for the battle to end.

Generally, completing 4 out of 6 quests is enough to win. But, the actual outcome hinges on the (unclear) battle mechanics of the gods, so your mileage may vary(you can tell when a good god is destroyed in the battle).