Here is the full list of all 31 Mountain achievements. It takes around 200 hours to unlock all of the achievements on Windows.
Mountain sings quite a lot
Mountain plays a lot of music
Mountain is home to many things
Mountain has a lot of alone time
Mountain is alive for a short time
Mountain has some alone time
Mountain organizes itself
Mountain makes it unrain
Mountain no longer trusts the weather
Mountain sings
Mountain is home to something new
Mountain cannot predict the weather
Mountain has unusual weather
Mountain thinks
Mountain survives death
Mountain experiences death
Mountain plays music
Mountain is bombarded by things
Mountain watches the days go by
Mountain sees it all come and go
Mountain dies several times
Mountain goes on dying
Mountain keeps surviving death
Mountain thinks it is invincible
Mountain experiences pain
Mountain experiences a lot of pain
Mountain thinks quite a lot
Mountain cannot stop thinking
Mountain lives for a long time
Mountain lives forever
Mountain keeps organizing itself