quests and major points of the story

The main goal is to find the key before anyone else, so what and where exactly is the key?
When the gods contained the The Devourer it created its own realm of imprisonment that is the astral plane. the Astral Plane continued to grow as the devourer shifted within the stars as essentially a ghost of the plane not strong enough to communicate or touch anything, but it watched the plane grow. However, when the plane was created, it created a key with it. the Key was meant as a way of opening the door once again to let the devourer out. The gods tried to destroy the key with no avail with each attempt the key would remain intact as part of the inevitable balance of the planes, so the gods hid the key.
The gods hid the key within one of their creations. A small child named Aurora that could hide within the astral plane and blend in with the rest of those that inhabited the plane. She would be followed and protected by a guardian- a sentient warforge named Vaelin that taught the child and watched over her for millennia. The warforge, however, is beginning to lose its grace and cannot protect the child as well as it used to. Hidden on a small floating island of other war forges, autognomes, and xions. The two live on Ironhold, a small floating rock that holds the different tech races that are also home to The Technomancers' Union which protects the mechs that live within the city.
The Call to Adventure- The players are invited to a celebration on Lumina by the Queens Eadric and Lyrisa at their home. The celebration marks the 500 years of Lumina and the wonders of the Astral Plane. Each of the players gets their own invite but they would all in the end know each other as being old adventuring buddies that got their start together. Once arriving each would have their own moments until they would spot another of the players, and then they would eventually realize they were all asked there for a reason.
Queen Lyrisa would lead you away from the party and to another section of the castle to discuss the issues plaguing Lumina and other parts of the Astral Plane. Lyris would take you to see her daughter, and she would explain that there is a sickness ravaging the plane that other governments are working together to control but it is becoming harder and harder, and her daughter has been affected by it as well. When seeing her daughter you would meet the other queen Eadric who sits and the end of the bed and another luminan sitting on the couch. Cassius is the advisor to the queens and is the highest advisor to the Starlight Enclave and he explains that there is a solution to the plague, but it is dangerous. He explains the Astral Key That can be used to restore balance to the astral plane, but others are looking for the key hoping to take the power for themselves and even disrupting the balance even further.
Lyrisa and Eadric ask the party to seek out the Astral Key in order to save their daughter and the Astral Plane from destruction. Cassius would be able to provide a better map of the astral Plane and invite the players to seek out council from the Astral Elves for further guidance.
the plot points and roadmap-
at some point, the party will have to have an encounter with the devourer's followers. they are ugly and void of color and will attack anyone looking for the key. these will be the main antagonists of the plot until we get to the main villain, Cassius who is in charge of growing the following and speaking directly to the devourer.
space pirate fights are key in this game. fights with the Giff military, the Githyanki on their red dragons, the some of the other rampaging pirates on the astral sea.
a meeting with a dying god who tells them about the devourer and what they did to trap them. This god would be on the verge of death and would tell the story of what the devourer is and how they sealed it away. this would be the quest that reveals that the key is in fact not a key but a child. he would send them to find the protector.
A fight with the bbeg foreshadows what is going to happen, and who it might be. this creates the race to the key.
they find the key before the others do and meet with the protector and Aurora who is still just a small child. She knows what she really is, but through the millennium has become something so much more. she has found through her abilities that she and the key are separate but the same, she can detach the key and show it to others. the players are then able to take the key and bring it to back to Lumina.
more fights now that they have the key.
if they haven't figured it out yet, then the players will take the key to Lumina and then Cassius would steal it and try to run away and fight the party. if the party realizes it's Cassius then they will come for the key and take it.
the party will adventure to the end of the astral plane to the door that would be used to let the devourer out. this would be the big fight against Cassius who would then be taken over by the devourer.
if they win then the small child would appear from the key, thanking the party and departing on her way.