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