You speak black speech, causing immense darkness to cover an area.

Magickal darkness spreads from a point you choose within range until the spell ends. The darkness spreads around corners. A creature with Darkvision can't see through this darkness. Nonmagickal light, as well as light created by spells of 8th level or lower, can't illuminate the area.

Shrieks, gibbering, and mad laughter can be heard within the sphere. Whenever a creature starts its turn in the sphere, or enters the spell's area for the first time on a turn, it must make a Wisdom saving throw, taking 4d8 Psychic damage and 4d8 Dark damage, and potentially become

Frightened

Critical Success (+10). The target is unaffected.
Success. The target takes half damage.
Failure. The target takes full damage and is Frightened of the imaginary creatures that appear to be present within the sphere until the end of their next turn. While Frightened by this spell, a creature cannot move intentionally closer to the sphere while outside of it.
Critical Failure (–10). As failure, except the target takes 1.5× damage.