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