Crest of the Forgotten Masters

The caster extends a hand, condensing their knowledge of ages past into a mote of dense arcana. The mote attaches to a single target within range, creating a tiny blue light on the chest. The mote can only be removed if time runs out, or by a 4th level or higher dispel magic spell. As a bonus action, the caster can detonate the mote, forcing the target to make an Intelligence saving throw. On a failed save the target takes 4d8 Psychic damage, and is stunned until the end of their next turn. On a successful save the target is not stunned.
If casting the spell at 5th level or higher, the damage increases by 1d8 for each level above 4th.