Your ability scores each increase by 1.

Unicorns reach maturity at around 30 years old and usually live up to 200. For the first 3 to 5 years of their life, unicorns stay in their unicorn form until one day they begin swapping between their unicorns and human forms. It usually take about a year for the child to gain full control over their transformations but it can take much longer or shorter depending on the child. 

Unicorns tend towards chaotic good alignments. They often enjoy helping others and value freedom greatly. 

Unicorns can vary widely in height and build, from barely 5 feet to well over 6 feet tall, just like humans. Regardless of your position in that range, your size is Medium in human form. In unicorn form, your size is large.

Your base walking speed is 30 feet in human form, and plus 50 feet in Unicorn form.

You can speak, read, and write Common and one extra language of your choice. Unicorns typically learn the languages of other peoples they deal with, including obscure dialects. 

As an action you can shift between Unicorn and Human form. When shifting form equipment can either fall to the ground, merge with the form (equipment has no effect while merged), or be worn by the form (equipment doesn’t change size, if it doesn’t fit the new form it must either merge or fall to the ground).

Unicorn Form - Size large, Speed 80ft, Unarmed strike deals 1d8 (attack with hooves/horn) and is considered magical

Human Form - Size medium, Speed 30ft

You have superior vision in dark and dim conditions, dim lighting within 60ft is bright light, darkness is dim light but is only seen in black and white

You know the Minor Illusion cantrip. When you reach level 3, you can cast the Purify Food and Drink spell once per day. When you reach level 5, you can also cast the Call lightning spell once per day. Wisdom is your spellcasting ability.