You are able to absorb the spirits of legendary astral creatures from across the land gaining new features to activate once raged

Combining Constellations

Starting when you choose this path at the 3rd level, Upon entering a rage, you can transform your body revealing the astral spirit within you. Once per turn as a bonus action, you manifest or swap one of the spirits inside gaining its power as it forms onto your body. All the spirits disappear once your rage ends or you fall unconscious.

Ursa Minor (The Little Bear) The small bear's spirit grows with your energy. Upon activation, your mouth forms into a bestial snout. Once per turn, directly after a successful hit, you can bite the target for an additional 1d4 damage. This ability strengthens based on the number of astral's inside you as shown by the table

Astral's	Dice
1	1d4
3	1d6
6	2d4
10	2d6

 

Leo (The Lion on Nemea) The impenetrable lion's spirit radiates out from you giving your skin a metallic golden look. You gain +1 bonus AC and temporary points equal to your barbarian level

Aquila (The Eagle) Your eyes begin to glow and crackle as your senses go on high alert. Gaining +5 to passive perception and advantage on perception checks 

Centaurus (The Centaur) Your feet round out into the shape of hooves and you feel immense strength in your legs. You can use the dash ability as a bonus action and gain +15ft of movement speed

Pegasus (The Winged Horse) A beautiful set of white wings extend from your back giving you 30ft of flying speed.

Hercules (The Hero)  Upon attaining Hercules' spirit, your body permanently grows in size, gaining more pronounced muscle and a  +1 bonus to your strength modifier. When activated Hercules's strength allows you to benefit from the versatile trait of weapons even when wielding in one hand.

Ursa Major (The Great Bear) The mother bear enhances her child, When activated alongside Ursa minor you regen hit points equal to the damage dealt by the bonus dice. When Ursa Major is summoned on her own, her bestial rage causes your hands to grow into massive paws. You drop anything you are carrying in your hands and can attack for 1d6 slashing damage on a hit. Once on each of your turns when you attack with a claw using the Attack action, you can make one additional claw attack as part of the same action.

Taurus (The Bull) The large bull spirit causes horns to protrude from your head. Your momentum in battle allows you to ram into opponents on a missed attack. Once per turn on a failed melee attack you can choose to headbutt your opponent. The target must succeed a dex saving throw (DC. 8 + Strength modifier + Prof. bonus) or take 1d4+ Strength modifier damage.

Orion (The Hunter) A belt clamps around your waist as you bring the hunter's spirit forward. You gain expertise in Athletics, Stealth, and Survival for the duration of the rage. If you choose Orion for Arcane Adapt you may only choose one of these skills to be present.

Aries (The Ram)  The golden Ram forms a beautiful wool mantle adorning your shoulders. Gaining the favor of the gods, you can now score a Critical hit on a roll of 19 or 20.

Andromeda (The Chained Maiden) An array of tattoos in the shape of shackles begin to form over your body. Your movement speed is reduced to 0 however as a bonus action on your turn you can make an additional attack. The damage of the attack does not benefit from your ability modifier.

Draco (The Dragon) The Dragon Ladon's immense power rips its way out of your back in the form of many of the serpent's heads. These heads nip and bite at your opponent distracting them and giving you a +2 to your hit bonus.

Cassiopeia (The Queen)  A spectral crown forms above your head causing your attacks to become magical

Star Sickness

Activating too many Astral creatures with "Combined constellations" takes a large toll on your physical state as the cosmic energy tries to escape. When having a number of Astral's Summoned greater than your proficiency bonus you begin to take 1d8 psychic damage per turn for each Astral over the limit. This damage cannot be reduced or blocked

Astral Adept

At 6th level, your body is becoming used to the comic energy inside you. You can keep one astral spirit activated outside of rage. It takes a minute of concentration to swap between them and can be done a number of times equal to your constitution modifier per day. This creature still counts towards your Star sickness number.

Reckless Transformation

Beginning at 10th level, While raging you may choose to speed up your astral transformations without care for the toll on your body. Activate two Astral spirits as a bonus action. If you  do this you take 1d8 psychic damage

Cosmic overflow

Starting at 14th level you have absorbed so much energy that your mind becomes unstable. After taking more than 30 psychic damage ....