Here is the full list of all 16 Great Old One - there are Arrival achievements.
Unlock all weapons
Upgrade one dragon to max level
Dance combo to 40!
Collect 10000 soul
Awaken any weapon
Defeat 1000 evil monsters
Defeat 1000 spiders
Defeat 1000 skulls
Defeat 1000 ratkins
Defeat 1000 zombies
Defeat 1000 guardians
Defeat 1000 automates
Defeat 500 monsters with sheild
Defeat 500 minions summoned by BOSS
Defeat 1000 aliens
Reborn 100 times