Events reached either during extreme focus or moments near death, you manage to glimpse the core of cursed energy. Breakthroughs take one of two forms.
Black Flashes
Channeling cursed energy into an attack within 0.000001, you cause a spatial distortion which emits black lightning. This event is called a black flash.
In order to land a black flash, you must land a critical hit. After landing a critical hit, you roll a second d20, on a natural 20 you activate a black flash. This causes the attack to deal 3 times the critical damage, and bypasses resistances, but not immunities.
Reverse Cursed Technique
Wish whoosh, reverse cursed technique processes negative energy into positive energy by taking two sources of cursed energy and multiplying them by one other.
After almost dying, be it being knocked out in one hit, or failing two death saves and then being revived. Those are moments where the GM can choose to bestow reverse cursed technique, alternatively roll a d100, on a 90+ you get Reverse Cursed Technique.
You learn to use your cursed energy in a completely opposite way, channeling positive energy instead of negative. You have a pool of healing you can use with your reverse cursed energy that’s equal to 5 times your level times your Charisma modifier. As a bonus action for X cursed energy, you can remove healing from that pool to regain hit points. You may also remove healing from the pool as a reaction to receiving damage once per round. For every 1 cursed energy spent, you regain 10 hit points, removing an equal amount from the pool. If you are suffering from a physical injury such as a concussion or something similar, one of these effects can be healed for every 10 hit points recovered with the reverse cursed technique.
You can use your Reverse Cursed Technique until your healing pool ends before getting burned out, during which you can’t use RCT until your healing pool recovers. At the beginning of every two rounds, you gain 10 hit points from your healing pool. Your healing pool automatically goes back to full at the end of a long rest, or short rest if you recover cursed energy on a short rest.