Long Game

While casting this spell, you must engage your target in conversation. At the completion of the casting, the target must make a Charisma saving throw. If it fails, you place a latent magical effect in the target's mind for the duration. If the target succeeds on the saving throw, it realizes that you used magic to affect its mind and might become hostile toward you, at the GM's discretion.
Once before the spell ends, you can use an action to trigger the magical effect in the target's mind, provided you are on the same plane of existence as the target. When the effect is triggered, the target takes 5d8 psychic damage plus an extra 1d8 psychic damage for every 24 hours that has passed since you cast the spell, up to a total of 12d8 psychic damage. The spell has no effect on the target if it ends before you trigger the magical effect.
A greater restoration or wish spell cast on the target ends the spell early. You know if the spell is ended early, provided you are on the same plane of existence as the target.