Web Trap

A 5 foot x 5 foot  square of ground you can see within range becomes clogged with spider web. Any creature that starts or ends its turn in this square must make a constitution saving throw or take 3d6 poison damage, and their speed is reduced by half until their next turn. On a successful save, their speed is still reduced, but they take no damage. The webs in the square disappear when the spell ends.