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