Blood Circle

Channeling the blood from either yourself, a corpse, or a willing participant within 15ft, you splatter the liquid around yourself on the ground in a 10ft radius. The creature who's blood is used takes 1d8 Necrotic damage. 

You decide what triggers the circle when you cast the spell, the most common trigger when casting is a creature stepping within the radius of the circle.

When you create the circle,  choose either Ensnaring grip or Spiked strike.

Ensnaring Grip. When triggered, the circle explodes into a mass of bloody tentacles, gripping at the legs of the creature who triggered it. Each creature in the area must make a Dexterity saving throw or be restrained until the end of your next turn.

Spiked Strike. When triggered, the circle erupts into a ring of spikes. Each creature in the area must make a Dexterity saving throw. A creature takes 3d8 piercing damage and 3d8 Necrotic damage on a failed saving throw. Or half as much on a successful one.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage of a Spiked Strike Circle increases by 1d8 for each slot level above 3rd