Even if you defeat Lv2000, the rainbow chest doesn't guarantee you to get Oracle. I've won twice and no Oracle at all. Luck matters, and in this game our luck often sucks.
I agree! It's a pain in the 🔥 to get through it and you may not even get a copy. They should have made it so Oracle can drop when you finish a raid against any Level. Not to mention one of Rex's better skills REQUIRES Oracle of the Sun on the field.