Here is the full list of all 33 Niffelheim achievements.
Collect 100 Golden Ore
Survive for 50 days
Kill 300 Skeletons
Cut down 100 Trees
Activate the Dragon
Use 20 different Potions
Craft 100 Alchemy items
Cook 100 dishes in the Kitchen Workshop
Craft 100 items in the Forge
Trade for 10,000 Gold
Upgrade all Workshops to 9 lvl.
Build all constructions of the highest level in a single Land
Build a lvl 1 stone Castle, Walls and Towers
Build a lvl 1 clay Castle, Walls and Towers
Eliminate 3 Bosses in underground caves
Activate 5 Charms
Kill 30 Spiders
Complete 3 quests of the Priests
Build a lvl 1 wooden Castle, Walls and Towers
Kill 10 Buffalos
Collect 10 Charms
Grow 200 Vegetables
Consume 10000 HP
Expose 10 Graves
Complete 10 Quests
Kill 10 Bears
Kill 1000 Skeletons
Inflict 25,000 damage with a long-range weapon
Kill 500 enemies with your Dragon
Survive for 100 days
Survive for 200 days
Reach Asgard at least once!
Reach Asgard in 100 days!