Here is the full list of all 39 Vikings - there are Wolves of Midgard achievements.
Complete Game+.
All Hunt maps complete.
Unlock all Gifts in Odin's gift tree.
Rage continuously for over 20 seconds.
Complete all Challenges on all maps.
Unlock all Gifts in Thor's gift tree.
Unlock all Gifts in Skathi's gift tree.
Complete the game as the Shieldmaiden.
Accomplish campaign in Valhalla Mode
Accomplish campaign in Valhalla Mode on highest difficulty.
Collect one of every rune.
Earn 50,000 gold by selling resources.
Unlock all Gifts in Tyr's gift tree.
Keep Draupnir for yourself.
Complete the game as the Warrior.
Complete the game on the highest difficulty.
Complete Campaign 3.
Kill four foes in a single attack.
Complete all Trials.
Found all Legendary Items.
Unlock level 4 of the Shipmaster.
Unlock level 5 of the Smithy.
Become chieftain of all the clans.
Complete Campaign 2.
Burn the Imperial Fleet.
Complete the Imp Hunt.
Earn 1,000,000 Blood.
Kill 100 Jotun.
Unlock all Gifts in Loki's gift tree.
Liberate Flotnar village.
Complete Campaign 1.
Travel to Utgard.
Survive the Mire-Witch's spell.
Equip three runes on a single item.
Complete any Hunt map.
Killed 500 Tomte.
Perform 1000 rolls.
Defeat the Jokul.
Defend Ulfung Village.