Northgard

This relic belongs to the Bear clan so start a new game, pick the bears and play as normal.

Once you've progressed in the game and mined some iron build a forge and you'll have the option of creating a relic. Select the Scabbard of Gram which costs 10 iron, 100 gold and 50 wood and once it's been made (it takes a while) you need to place it somewhere in your lands to pop the achievement.