Arcane Hubris

Using sheer force of will, you can attempt to cast a spell that you do not know or have prepared. The spell you choose must be of a level for which you have a spell slot. You spend 3 sorcery points, as well as a spell slot to cast the spell, but before resolving it you must make a Charisma (Arcana) mixed skill check (use your CHA mod plus proficiency bonus if you are proficient in Arcana). The DC is 10 + twice the level of the spell slot you expend to cast the spell.

On a successful check, you cast the spell as normal, using your spell save DC and spellcasting ability modifier. On a failed check, you take 1 point of force damage per spell slot level and cast a different spell from the one you intended. Your DM randomly determines the spell you cast, which will be the same level of the spell slot you expended. If the slot is 6th level or higher, the result will be a 5th-level spell.

If you try to cast a cantrip you don't know, you spend 1 sorcery point, and make a DC 10 Intelligence (Arcana) check. On a failed check, there is no effect.