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