Here is the full list of all 28 Black Skylands achievements.
Defeat Horos
Defeat Ruth
Liberate All Islands
Defeat Kain
Defeat the Devourer
Obtain Steel Condor Crossbow
Visit Swarm Territory
Defeat Rhoda
Defeat Blast
Get more than 17 000 Weapon Steel
Get more than 17 000 Ship Steel
Get 50 Weapon Mods
Defeat Mort
Find 10 Chests of Gold
Get more than 6 000 Ship Steel
Liberate 10 Islands
Get more than 6000 Weapon Steel
Defend the Moth Village
Find 5 Chests of Gold
Get 5 Weapon Mods
Get more than 1000 Weapon Steel
Defeat Crash
Get more than 1000 Ship Steel
Liberate Mills Island
Liberate 3 Islands
Complete the Prologue
Get All Weapon Mods
Find All Chests of Gold