This spell allows the user to transform The soul of the zodiac, and gain immense power. The user will have to roll a d12 but when the user hits lvl 17 a new zodiac form will be available. The 13 Zodiac is called the Zodiac of the serpent. You will have to work with your dm to find a way to make this zodiac mode work. Be it a little op because it gains the powers of all 12 Zodiacs in one. all the ability will be down below.

Aquarius-

When you are in your Aquarius Mode. You're no longer someone on earth. Your body becomes water and you gain a flying speed of 30ft. 

Pisces-

When you are in the Pisces Mode. You gain the ability to Breed underwater and a swimming speed equal to your walking speed. In this mode, you can talk to animals

Aries-

When you are in the Aries Mode. as an Action all allies in 30ft of you will gain 1d12+Int mod to their Temporary hit points. 

Taurus-

When you are in the Taurus Mode your Ac and STR gain a +2. And you will have an additional d8 Dmg to your unarmed attacks.

Gemini-

When you are in the Gemini Mode as an Action you can copy the ability of a creature for the spell's duration.

Cancer-

When you're in Cancer mode. You become a Samurai and you will gain a sword made of stars that can do 3d12+ STR mod Dmg. 

Leo-

When you’re I’m Leo mode you become light, all your attacks will deal radiant Dmg and your Ac will increase by 2.

Virgo-

When you are in the Virgo Mode you gain a Burrowing speed equal to your walking speed. and you gain the spell Earthquake. you can only use this spell amount of times equal to your Intelligence.

Libra-

When you are in Libra Mode you can use something called wild magic, if you used any spells and rolled a natural 17 the target you hit will have to roll a d100 from the wild magic table. And whatever they roll on they will be under it for one minute.

Scorpio-

When you are in the Scorpio Mode, your speed increases by 10. And when you are in a Desert Area you will be able to go invisible for 5 minutes. And if your allies are within 30ft of you. You can spin an Action to make them invisible.

Sagittarius-

When you are in the Sagittarius Mode. You will add 200 ft to all your Range attacks. If you are using a longbow you can use an Action to shoot multiple arrows at once. (Maximum of 5)

Capricorn-

When you are in Capricorn mode, your STR and speed will increase by 3. You will have an additional d8 to your unarmed attack. And ask long as you in this form you can be charmed or put to sleep.