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