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