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