Elemental Shell Rune

   Upon casting this spell, target a point wtihin range. A small rune appears on the floor at the designated point. The spell is triggered when a creature walks within 5 feet of the rune. The creature that triggered the rune, as well as any other creatures within 15 feet of the rune makes a Strength saving throw. On a failed save, that creature is confined within a one half inch shell of the material it is standing on, or remains free if they pass. A target entombed by this spell can make another saving throw against this spell at the end of its turn. If the target is standing on snow, they are contained in ice. If the target is standing on sand, they are contained in hardened glass. If the creature is flying, they make their strength saving throw at advantage. If a flying creature fails its saving throw, it plummets to the ground at a rate of 30 feet per round.

   A creature that remains entombed by this spell for a duration of one minute must make a Constitution saving throw. If they fail the saving throw, they are knock unconscious. if another minute passes within the shell, they drop to 0 hit points. If they remain within the shell for another minute, they die. Any creature that does not need to breath is only knocked unconscious.  In order to attempt to break the shell, a creature that is outside of the shell must make a Strength check to break the shell. The DC depends upon the material of the shell: 19 for any kind of stone, 17 for ice and 15 for hardened glass.