In the season finale David is once again wearing the triangle shirt which symbolizes David finding himself. We can see this in how David is in complete control of 90% of the narrative in Chapter 9. While David has truly found himself, Cary explains that David is only able to do so because the tech head band David is wearing has locked the Shadow King in Davids sub conscious. Just as David can not go around wearing the head band the rest of his life, it will only be a matter of time before the parasite which is the Shadow King figures out a way around David's sub concious and kills David.
While all above is being explained Syd has a run in with the Shadow King who tells her that if Syd helps the Shadow King escape David and find a new host, she will allow David to live. At this moment it was pretty obvious that with Syd's powers and love for David she was going to have to trust the Shadow Kings word in order to save Davids life.
From here Cary begins working on the risky task of removing the parasite known as the Shadow King from Davids brain. While cary is doing this, we walk through David's life from childhood to present seeing memories and moments the Shadow King created being erased. Just as Cary thinks he has killed The Shadow King, the parasite starts to fight back and in the process is obviously killing David. This springs Syd into action! Syd runs into the room David is in and kisses him on the lips. This gives the parasite the oppurtunity to jump from David to Syd.
As soon as The Shadow King hops into Syd the parasite immidetly makes it's way to Kerry (the combat member of the group) and quickly desposes of threats coming from the rest of the team. From here it seems as if the Shadow King is content on using Kerry as it's new host until confonted by David in a hall way. From here the final battle between The Shadow King and David commences! In one of the most epic super hero scenes on TV, David via psyonics drives The Shadow King out of Kerry. Once out of Kerry, The Shadow King needs a new host and quickly finds Oliver and attaches it's self to him. While this may seem like another problem in which David has to fix, the truth is Oliver was not all there.
Oliver had basically lost is mind and the only thing that was left was his physical form. This made Oliver the perfect final landing spot for the Shadow King because it gave the Shadow King a host body who's mind was no longer there.
The last scene shows Oliver happily driving alone in his car. As the camera pans accross the wind shield reaching the passanger side, we see in fact that Oliver is not alone. The Shadow King is there and has attached itself to Oliver.
Final Scene Explained & Next Season Leaks
In the final scene of the season finale David and Syd are standing talking and sharing a romantic moment on a balcony when a metal orb drone shows up. Davids last words are " oh fu" as he is sucked inside.
Leaks have cone forth that next season David and team will be dealing with Division 2 and division 1. Higher levels of government operations than division 2 as explained by The Interragator. In addition the main villian next season will once again be none other than Oliver and The Shadow King who appear to be in the process of searching for professor Xavier now.
The show producers have also stated next season will run 10 episodes opposed to this seasons 8. In addition the writers have said be prepared for more action and use of powers as Legion will start shifting more towards New Mutants and X-Men orgins. With that being said, producers and writers have stated not to expect any story lines pulled from the comics but rather ideas and characters from the comics with in creative new stories.
One last spoiler I have on good word of another villian we may see next season....