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