Here is the full list of all 39 Vikings - there are Wolves of Midgard achievements.
Complete the game as the Warrior.
Complete Campaign 3.
All Hunt maps complete.
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.
Complete the Imp Hunt.
Earn 1,000,000 Blood.
Unlock all Gifts in Tyr's gift tree.
Kill 100 Jotun.
Liberate Flotnar village.
Equip three runes on a single item.
Complete Campaign 1.
Travel to Utgard.
Survive the Mire-Witch's spell.
Kill four foes in a single attack.
Killed 500 Tomte.
Complete any Hunt map.
Perform 1000 rolls.
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 Skathi's gift tree.
Unlock all Gifts in Thor's gift tree.
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.