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