Touch of Stygia

You make a melee spell attack with the rapier. On a hit you plunge the rapier deep within the creature. The target must make a Con save, on a success the creature takes 4d8 cold damage and takes no further effect. On a fail the creature is restrained and begins to freeze taking 4d8 cold damage. At the beginning of the creature's turn it must make a Con save on a success the creature takes 4d8 cold damage and the spell ends. On a fail the creature takes the same damage and is frozen in ice. While frozen this way it is considered petrified, is immune to all further damage. A wish, divine intervention or the fates card can reverse this effect.