The The Taken King Add-on for Destiny has 10 achievements worth 250 gamerscore.
Complete the King's Fall Raid (Heroic).
Complete the "Echoes of Oryx" quest.
Complete "The Sunbreakers' Challenge" quest.
Complete "The Stormcaller's Path" quest.
Complete "The Old Hunger" quest.
Complete the King's Fall Raid.
Complete "The Court of Oryx" quest.
Complete "The Wolves of Mars" quest.
Complete "The Taken King" quest.
Complete "The Nightstalker's Trail" quest.