When you reach Prestige 4 you can teleport to Act 3 experience zone.
➜ How to teleport?

On Act 3 there are 4 level zones HLVL C1-5, HLVL C5-10, HLVL C10-20 and HLVL C20-30, in which you can reach up to +30h.
This will follow the same proccess as before, you will need to reach the maximun level to continue to the next level zone.
When you reach Hero lvl +30, you will need to use $prestige command to become Prestige 5. You will get back down to Hero lvl +1 and you need to level up to Hero lvl +30 again in order to use $prestige again and become Prestige 6.

On this zones the monsters will drop Rare Crystal materials, that will allow you to craft equipment and stuff.
As a recommendation, you should craft Weapon Skin that will give you +3% attack and Partner Specialist Card to imporve your partner!
Act 3 also includes Farming zones where you can get materials to upgrade SPs Angel Feathers and Full Moon and Gold.
Last but not least, on this zone you will be able to craft 25h Equipment, that will make you really strong against coming monsters.