Arachnophobia

The target must roll a Wisdom saving throw when the spell is cast and again at the end of each of its turns or be considered frightened for the duration of the spell, the source of fear being thousands upon thousands of illusory spiders that cover the target's body. On a success, the spell ends. A creature that is a construct, undead, or immune to the Frightened condition succeeds this saving throw automatically. While under the effects of the spell, the creature must use its action to attempt to brush off the spiders.