The wizard that created the spawning mirror believed that, since created from a mirror, these beings would be incredibly fragile for a living being. So, he gave the race an increased ability to hold against hits. Their Constitution is increased by 1. Since created by magical means, the race gets an increase to their Wisdom of 2

Since they are created by magic, this race lives for around 200 years, reaching adulthood at 50.

Since you are a reflection of a being, you can speak two languages that they can speak.

Once per long rest, you can reflect a spell of 3rd level or lower back at the user. To do so, you must roll a d20 above the DC. To determine the DC, add 13+ the spell's level. At 10th level, you can use this ability twice per long rest.

When in front of a clear glass mirror, you can open a gate to the mirror plane. Any item or being that touches the mirror gate is instantly transported to the corresponding mirror in the Mirror Dimension. This gate stays open until you cancel it. 

You can cast Minor Illusion at will. At 5th level, you can cast Disguise Self once per long rest. At 10th level, you can cast Shatter once per long rest.