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