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