Crystal Elemental

Prismatic. The elemental's crystalline form is resistant to magic and can reflect or rebound spells that are cast at it.

Fragile. The elemental is vulnerable to Bludgeoning damage.

Multiattack. The elemental makes two attacks, using Slash or Spike Launch in any combination.

Slash. Melee Attack Roll: +7, reach 5 ft. Hit: 11 (2d6 + 4) Slashing damage.

Spike Launch. Ranged Attack Roll: +7, range 60 ft. Hit: 7 (1d6 + 4) Piercing damage.

Spell Reflection. Reaction. If the elemental makes a successful saving throw against a spell, or a spell attack misses it, the elemental can use its reaction to target another creature (including the spell caster) it can see or sense within 60 feet of it.

The spell targets the chosen creature instead of the original target. If the spell forced a saving throw, the new target creature makes its own save. If the spell was an attack, the attack roll is re-rolled with original modifiers against the new target.