Spellbound Soul

Pre requisites:
Spell Caster and 18 or higher in your spell casting ability.

As a caster that understands your limits, you look for a way to break those limits. You can reach beyond the normal mind of a caster to conjure a spell unfamiliar to you. You're allowed to cast a spell from your spell list that you don't know or have prepared. Before the spell is cast, make a saving throw with your spell casting modifier. The DC is 10 + double the spells level your attempting to cast. If you fail the saving throw, a wild magic surge goes off instead of the spell desired.
You can do this as many times equal to half your proficiency bonus rounded down per long rest.
(Ex: 1st level: 1 time, 9th level: 2 times, 17th level: 3 times)