Here is the full list of all 39 Vikings - there are Wolves of Midgard achievements.
Complete all Challenges on all maps.
Complete Campaign 3.
Complete the game as the Shieldmaiden.
All Hunt maps complete.
Found all Legendary Items.
Unlock level 4 of the Shipmaster.
Complete all Trials.
Unlock level 5 of the Smithy.
Kill 100 Jotun.
Unlock all Gifts in Skathi's gift tree.
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.
Liberate Flotnar village.
Complete Campaign 1.
Travel to Utgard.
Survive the Mire-Witch's spell.
Equip three runes on a single item.
Killed 500 Tomte.
Complete any Hunt map.
Perform 1000 rolls.
Defeat the Jokul.
Defend Ulfung Village.
Complete the game as the Warrior.
Complete Game+.
Keep Draupnir for yourself.
Kill four foes in a single attack.
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.
Unlock all Gifts in Thor's gift tree.
Collect one of every rune.
Accomplish campaign in Valhalla Mode
Accomplish campaign in Valhalla Mode on highest difficulty.