1. Being Level 60 and above Summonner Class, and talk to NPC "Challenge from the summoned monster" in the Quest/Dungeon Reception Map.
Choose "Challenge from Gilgames"
and battle agasinst God of the Sword Gilgamesh !
You will be able to receive 1 "Hero Stone"
item necessary in order to change class.
If you are already reached to Lv 60
or above with Summoner, collect "Hero Stone" and other necessary items
and head over to Advanced Class NPC and unlock "Iroas" to change class !