Bone Prison

You throw the bone fragments, causing a cage of bone spikes to sprout from the ground in a circle with a 5 foot radius. The bone spikes are 10 feet tall, and merge to a point above the middle of the circle. The cage is Armor Class 18, has 30 hit points, and is resistant to necrotic, fire, cold, and lightning damage, and is immune to poison and psychic damage. The cage cannot be moved through without breaking it.

When you cast the spell, any creature that is completely inside the cage's area is trapped. Creatures only partially within the area, or those too large to fit inside the area, are pushed away from the center of the area until they are completely outside the area, taking 4d8 piercing damage and being knocked prone.

The cage provides no cover for a creature trapped in it. A large creature trapped in the cage is restrained. A small creature stuck in the cage can squeeze out with a Dexterity check, the DC of which is your spell saving throw DC, and a tiny creature cannot be trapped in the cage, as it can simply move between the bars.

The cage lasts for the spell's duration, at the end of which it crumbles to dust.