The Isle of Sgàil Add-on for HITMAN 2 has 7 achievements.
Complete The Ark Society on Master Difficulty.
Take the scenic route.
Reach Isle of Sgàil Mastery Level 20.
Complete all Mission Stories in The Ark Society.
Select a Starting Location and use an Agency Pickup to smuggle an item into Isle of Sgàil.
Complete The Ark Society.
Trap Zoe in the effigy, strangle Sophia with the necklace, force the Constant to come quietly.