Displacer Beast's Power

You have developed traits reminiscent to that of a Displacer Beast, granting you the following benefits:

• You learn the mirror image spell. You can cast this spell without expending a spell slot. Once you cast this spell in this way, you can’t do so again until you finish a long rest. You can also cast this spell using spell slots you have.
• When you are subjected to an effect that allows you to make a saving throw to take only half damage, you can use your reaction to instead take no damage if you succeed on the saving throw, and only half damage if you fail. You can use this feature a number of times equal to your proficiency bonus, and you regain all expended uses when you finish a long rest.