Wrath of Entropy

You wreathe yourself in a storm of cosmic ice shards. It lasts for the duration. All creatures within 10ft of you when you cast the spell must make a Dexterity saving throw. On a failure, the target takes 8d8 cold damage, or half as much on a successful one. For the duration of the spell, any target that enters this range, or ends its turn there must repeat the saving throw. The ground within range is considered difficult terrain for anyone except you. 

For the duration of the spell, you gain a number of charges equal to your spellcasting modifier, a minimum of 1, which you can use to cast the spell Entropic Bolt at Level 1 as a bonus action. Each casting consumes one charge. Consuming all charges ends the spell.