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