The caster furiously swipes the air in front of him tearing reality apart in the form of a window to the far realm making anyone in 20 feet cone in front of him to catch a glimpse of the horrors of that maddening dimension.
Anyone in the range of the spell must make a Wisdom saving throw against your spell save DC. On a successful save the victim fools himself to believe that what he saw was merely an illusion and is not affected by the spell, on a failed save the victim takes 7d6 psychic damage and must roll once in the Short-Term Madness table. At the end of each turn, a character affected by a short term madness effect can use its action to repeat the saving throw and get rid of the effect.
If you cast this spell with a spell slot higher than 4 increase the damage by 1d6 for every level above 4, additionally increase the distance by 5ft for every spell slot level used above level 4.
If you cast this spell with a level 6 spell slot or higher roll in the Long-Term Madness on top of the short term madness.
If you cast this spell with a level 9 spell slot roll once in the Indefinite Madness table, roll twice in the Long-Term Madness and twice in the short term madness table (each of the short term madness effects requires a different save to prevent or get rid off).