Here is the full list of all 39 Vikings - there are Wolves of Midgard achievements.
Complete the game as the Warrior.
Complete Campaign 3.
Unlock level 4 of the Shipmaster.
Unlock level 5 of the Smithy.
Become chieftain of all the clans.
Unlock all Gifts in Tyr's gift tree.
Unlock all Gifts in Odin's gift tree.
Complete Campaign 2.
Burn the Imperial Fleet.
Unlock all Gifts in Thor's gift tree.
Complete the Imp Hunt.
Unlock all Gifts in Loki's gift tree.
Kill four foes in a single attack.
Unlock all Gifts in Skathi's gift tree.
Earn 1,000,000 Blood.
Equip three runes on a single item.
Liberate Flotnar village.
Kill 100 Jotun.
Complete Campaign 1.
Travel to Utgard.
Survive the Mire-Witch's spell.
Complete any Hunt map.
Killed 500 Tomte.
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.
All Hunt maps complete.
Found all Legendary Items.
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.