Agitate Blood

Make a ranged spell attack against one creature that can bleed within 30 feet, dealing [roll]3d8[/roll] magical piercing damage on a hit. The sliver of red energy burrows into your target's body, causing their blood to react violently.

While the spell persists, and if the creature isn't undead, you may cause the agitant to attack their blood, causing it to squirm and twist violently inside their veins, interfering with their actions. When you see the target take an action, you may use your reaction to cause the agitant to pulse. This deals an additional [roll]3d8[/roll] necrotic damage. The creature must succeed on a Constitution saving throw or suffer disadvantage on the next attack, save, or skill check roll the creature makes before the start of its next turn (including the action it was about to take).

At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, the piercing damage increases by 1d8 for each slot level above 4th.