Star-Crossed Wizard

When natural magic & sacrificial magic merge into a power that defies fate; with the power of a burning star; a Star-Crossed Wizard is born. Using elemental, holy, divine, or any other form of naturally gained or used magic, along with demonic sacrificial magic which uses life force; both magic's potency is dramatically increased. While most users of this type of power quickly die from the sacrificial magic; or are killed for learning it in the first place; a certain amount of people in a millenia can learn to master it. 

 

"It is said that the star crossed wizard herself; the queen to be of the Fey; used this technique alongside her immortal lifespan to constantly surpass her limits and become one of the most powerful figures ever known."

Starry Eyed Nightmare

Beginning when you select this subclass at 2nd level, The demonic nature of your magic and any items you have can no longer be detected by those who would be able to find it, no perception, investigation, or any other type of roll can discover the presence of your demonic magic, and any charisma based check has a fixed +5. At level 6, roll a d6. The number you get determines the amount of characters you may share this ability with.

Demonic Fey Harmony

Starting at 2nd level, the demonic energy in your body tears your life force away, eating away at your flesh. Your immortal body recovers from this, however. Through the repeated cycle of injury and recovery, your endurance and pain tolerance increase. At each 2 level interval including this level, your constitution will increase by 1.

Blessing of the Stars

Beginning at 2nd level, your divine powers from the Tome of Feys to protect all those around you, when a spell is cast on allies within 100ft of your character, you and them may choose to have you roll their saving throw instead of them, using your stat bonuses/abilities/proficiencies. 

Using your demonic tome to siphon your own life force, you may use your constitution instead of any dice roll that would require strength or dexterity, though this is not required. 

Fate Intervention

Starting at 6th level, channeling the power of two completely separate types of magic can cause time to momentarily rewind, leaving the memories of those who you wish intact, while your enemies unknowingly repeat what they've done. When a creature succeeds on a saving throw against an ally's action, you may have all creatures who rolled for the action reroll. You may also cast this to rewind time by 2 seconds for any other reason. You must wait at least a long rest before using this ability again.

Dark Supernova Strength

Beginning at 10th level, mastering the art of sacrificial magic, you can add your constitution modifier to the damage roll of any spell you cast.

Endless Divine Void

Starting at 14th level, having mastered Fey and Demon magic in perfect balance, you must release a shockwave of energy across the entire battlefield in order to use your magic, lest you constantly exude and waste power. While active, every spell casting creature in range can only cast spells that are 1/3 (rounded down) of their initiative in level. This is regardless of their resistances, immunities, class, or race. The effect lasts for two rounds at the beginning of a combat encounter.