A huge, spectral crossbow appears, hovering over the caster's head. To see the crossbow, a creature must make a DC 13 Wisdom saving throw. On a fail, the crossbow has advantage on attack rolls on that creature. If it succeeds the saving throw, it can spot the crossbow at any time. During the casting of this spell, the caster can specify who is safe from the crossbow, and who is a target. The crossbow only attacks the targets specified during the casting. The targeted creatures cannot be altered at any time after the casting. However, the crossbow can be dispelled by the caster at any time. The crossbow cannot be re-summoned without expending another spell slot. 

The crossbow can attack up to three targets at a time. It attacks at the start of every of the caster's turns. It deals 2d10 piercing damage, 1d8 force damage, and 2d8 necrotic damage. In addition, if the targeted creature is Medium or smaller, OR the attack roll is a critical hit, the targeted creature is stunned. A creature  stunned in this way more than three times is immune to this effect for 24 hours. If the attack roll is a critical AND the creature is Medium or smaller, the creature is knocked unconscious. 

The crossbow has 100 hit points, and is immune to all damage except for necrotic, radiant and force. If destroyed, all targeted creatures take 1d10 necrotic damage, and this spell cannot be cast for 24 hours.