If vanitas

[Ceriraye 485]

If vanitas shows up in kh3

(Hopefully)

How do u think he will come up or appear?

[Hamzah-light 35]

mostly, in castle oblivion as a boss while saving ventus

[RoxSox 3,593]

mostly, in castle oblivion as a boss while saving ventus

That makes a startling amount of sense.

[HarLea Quinn 26,501]

As one of the 13 darknesses

[Ceriraye 485]

That makes a startling amount of sense.

Ikr 0.0

[Oblivion16 82]

As one of the 13 darknesses

What she said!

[jorrell3946 70]

In Castle Oblivion to explain to Aqua Ven and Sora how he was able to return. And Sora will be shocked the he is seeing himself.

[The Rocky Shoe 169]

He'll be in Castle Oblivion waiting for them and when they come in, the door will be sealed, he'll laugh the same way he did when he was fighting Ventus, and start explaing his plan or something.

[PrinceNoctis 1,011]

As a Seeker of Darkness!

[LeYenrz 276]

i don't think he'll be in the game, since his appearance in ddd was only an illusion. but he might appear as a small cameo in kh3 probably not as a full out boss. 

 

but if he did come in the game...he could be revived by Xehanort once more from the darkness of sora's heart and mix it with ventus' light and he could reappear. and then he'd use him to fight sora and riku and delay them from finding the 13 lights before he gets ready for the battle.

[Rob 5,571]

As a badass

[Allpro11414 71]

i think its quite obvious that hes gonna be in the game in some shape or form because they wouldnt have bothered even showing him in DDD, and another thing is that this incident is caused by Ventus' heart reacting within Sora which allowed him to see Vanitas so that could mean that Master Xehanrt has Vanitas 

[Jake 1,488]

mostly, in castle oblivion as a boss while saving ventus

Yah i agree he probably tries to prevent people to save him and when they reach where ventus is he would pop out and threaten him or her or the group and then if its a group then the whole group would be trapped out of the fight and vanitas fights sora and sora well.... you know

[DarkAvenger 88]

Through Sora in some way

[Dave 5,715]

He will show up, and proceed to taunt Sora. And then talk some more. And then taunt. And then laugh. And then taunt.And then, finally, he'll attack. And fail. So he'll go back to talking.

 

Rinse and repeat at least five more times.