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