One of my players is a demonologist and requested a cantrip related to the field. So I took a crack at it and came up with the following thinking that an attack on the mind was fitting:
Three Word Curse: Nails
Casting Time: 1 action
Range: 60 feet
Components: V, M (a fragment of ram horn)
Duration: Concentration, up to 1 minute
You speak in a demonic tongue slowly cursing the mind of a creature you can see within range. If the target can hear you (though it need not understand you), it must succeed a Wisdom saving throw to end the spell. On each of your turns for the duration, you may use your action to have the target attempt the Wisdom saving throw again. The spell ends if you use your action to do anything else. On the third failed attempt by the target, it experiences the feeling of several nails piercing their skull simultaneously and takes 5d8 psychic damage, and the spell then ends.
The spell’s damage increases by 1d8 when your reach 5th level (6d8), 11th level (7d8), and 17th level (8d8).
Does the risk of wasting the invested time balance the high damage reward?