Brightstones Ring of Challenges

You summon a ring with a radius of 20ft around you and one creature of your choice, the creature must make a Wisdom saving throw against your Spell DC to leave the ring.

If the creature succeeds, it suffers 1d8 Force damage by crossing the border of the Ring, additionally the spell fades.
If the creature fails, it is trapped in the ring with you, but may try again next turn.

When you leave the ring or fall unconscious the spell disappears.
No other creature, spell or projectile can enter through the borders of the ring and vice versa.