Here is the full list of all 43 Warden: Melody of the Undergrowth achievements.
Collect all 15 Health Crystals
Collect all 27 Lore Logs
Solve all 8 Riddles
Best 15 Mudmen
Solve the puzzle in the Sewer Adjunct
Destroy the Crystal in the Factorum
Open the Gatehouse to the Climb
Unlock Tavian's Sling
Best 15 Meretian Soldiers
Destroy the Crystal in the Buried Pyramid
Best 30 Tsarr
Collect a total of 2000 individual motes
Purchase a weapon costing at least 150 motes
Unlock Warden Form Bitt
Collect 5 Health Crystals
Collect 10 Lore Logs
Solve 3 Riddles
Destroy the Crystal in the Forest Grove
Stun an enemy with a Warden Power
Get slain in combat
Best 100 enemies in combat
Equip a tier 3 weapon
Best 30 Tusk Clan Polto
Have a conversation with another Warden's ghost
Light 5 campfires
Best 50 enemies in combat
Best 20 plant enemies
Defeat a Polto by knocking them off a ledge
Unlock Warden Form Medeira
Collect a total of 500 individual motes
Solve your first Riddle
Rescue the Bark Clan Shaman
Meet the Old Hoarder
Meet the Bark Clan trailblazer, Scout
Best 10 enemies in combat
Collect your first Health Crystal
Wear out a weapon until it breaks
Light 5 braziers in one level
Equip weapons in all 3 weapon slots
Collect a total of 100 individual motes
Collect your first Lore Log
Speak to Nyona
Become seperated from the Emperor