Here is the full list of all 8 Roots of Yggdrasil achievements.
Complete a loop with 7 cards or less into your Deck.
Meet Hoenir
Complete your first loop.
Have 15 or more curse cards into your Deck.
Build the Workshop in the Holt.
Build the Greenhouse in the Holt.
Witness Lif and Thrasir's Feelings Sprout.
Complete a loop with 50 cards or more into your Deck.