The Zaros godsword is the second strongest godsword in the game next to the Seren godsword. This godsword is obtained by finishing Desert Treasure and The Unbinding of Zaros. If you have finished these quests you can go to the God Wars Dungeon and kill any one of the bosses. Once you have killed one of the bosses in your chatbox it will read "The ground starts rumbling and a giant hole appears right beneath your feet... Something smells magically evil..."