Here is the full list of all 33 Skycliffs achievements.
Complete the tutorial
Reach Bluish forest for the first time
Reach Bluish forest 25 times
Reach Lunar ridge for the first time
Reach Lunar ridge 20 times
Reach Cracked lands for the first time
Reach Cracked lands 15 times
Reach Wetplains for the first time
Reach Wetplains 10 times
Reach Crystal palace for the first time
Reach Crystal palace 5 times
Discover Lunar temple
Discover Solar temple
Discover Water temple
Discover Scarlet temple
Carry all three holy marks at once
Defeat the Crystal golem
Win 5 races
Pass 5 weather studies
Win 5 lunar balls challenges
Unlock shortcut to Lunar ridge
Unlock shortcut to Cracked lands
Unlock shortcut to Wetplains
Unlock shortcut to Crystal Palace
Complete 25% of journal
Complete 50% of journal
Complete 75% of journal
Fully complete the journal
Defeat the Scarlet golem
Sacrifice on the lunar altar and survive
Win 5 Ice urchins awakening challenges
Clear 3 islands in a row with only 1 health point
Play the flat islands gamemode