Elemental Sunder

Choose 1 creature you see in range. The creature makes a Constitution save. On a failure, for the duration, the creature loses any of its resistance to elemental damage, or if it has immunity to those damage types, you can instead choose to have its immunity become resistance. On a success, the creatures lose resistance to your choice of elemental damage for the duration. If a creature isn't resistant to the chosen damage type, you learn this but can't choose a different type.