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