About Chaos Scrolls?

How can i obtain those without gacha?
Like what monsters has the higher drop rate for those?

 

You have a kill a Mini Boss called Lyka for a small chance at one. No other monster drops them and there's no other way other than gaching at Mushroom Shrine.

 

You sure? The monsters on hidden street prebigbang are either? they deleted it from the code?

 

Yes. None of those monster drop them. Use this link as a drop table reference:
http://library.royals.ms/