Thoughtseize

This forbidden spell is a product of the summer court of the Feywild, and such magic is not to be trusted.

When you cast this spell, you immediately take 2d10 Psychic damage, which cannot be resisted or reduced in any way. (This damage does not force you to make a concentration check.) 

A target of this spell must make a Wisdom saving throw or be forced to forget an available spell of your choice until the spell ends.

You then learn what spells the target knows, if any.

At the end of each of their turns, the target can make another wisdom saving throw to end the effect.

Artist credit: Aleksi Briclot