Here is the full list of all 20 The Clans - there are Saga of the Twins achievements.
Defeat the final boss.
Beat the 15th Testing Chamber.
Defeat Bob the Crimson Spider.
Defeat the Guardian Spirits.
Defeat the turtles.
Defeat Project X
Defeat Demon Master.
Defeat Stone Guardian.
Defeat Skeletard.
Defeat Ex-Mayor.
Defeat Chimera.
Defeat Onyxus.
Defeat Tormentor.
Win a battle.
Loot a chest.
Exit the bar.
Get rewarded by Sachiko.
Defeat Alpha Omega.
Defeat the final boss on the Ahaha difficulty level.
Defeat the Alpha Omega on the Ahaha difficulty level.