Cinder Ring

You create an ignis ring on a solid surface within range. You can make the ring up to 20 feet long, 10 feet high, and 1 foot thick, or a egg shaped circle up to 6 feet in diameter, The ring is opaque and lasts for the duration.

When the ring appears, each creature in its area makes a Dexterity saving throw, taking 5d8 Fire damage on a failed save or half as much damage on a successful one, trapping multiple creatures for one round