Here is the full list of all 38 Okhlos achievements.
Heal 43 plagues
Defeat Dyonissus without killing any of his summons
Unlock the special ending. No more Monty Python jokes, we promise.
Defeat all the subbosses
Perform 10 perfect blocks in a row
Finish a pacifist run
Break 55 smoke emitters
Defeat the Philosopher God
Defeat all the gods
Unlock the statues of the twelve Olympian gods, and then break them
Activate 7 diferent Cryptos
Defeat Zeus
Unlock one of the secret subbosses
Destroy 75 or more buildings in one world
Defeat Hades
Finish Lemnos
Finish a world without losing any people.
Kill more than 50 enemies in the same level
Finish Athens
Defeat a boss with 5 or less people in the mob.
Finish Atlantis
Finish Sparta
Finish Ephesos
Get a mob with 50 or more phantoms in it
Finish Delphi
This one is on the house. You are gonna have to work for the rest though.
Unlock all the heroes that were on board the Argo
Unlock all the heroes that took part in that epic and poetic war
Unlock all the philosophers of Rapahel's painting
Unlock all the persistent heroes and philosophers in the Agora
Unlock all the heroes
Have Elektra, Oedipus and Narcissus in the mob at the same time
Beat Hades in under 25 minues
Finish 3 worlds without destroying any buildings
Defeat 100 Hecatonchires
Beat the game without using any items
Beat the game with a mob capacity of 30 or less
Unlock all the entries in the encyclopaedia