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