While in Sora's Dream, Riku encounter's Ventus' Armor clad in black as a Nightmare, but was it Ventus' Sentiment trying to protect Sora, or Sora being possessed by the darkness within the armor?

 

By the way, Why did Ven smile at the end? I thought he was asleep. There could be many reasons to why he smiled.

Armor was protecting Sora which ended up getting possesed by the nightmare.

 

Ventus smiled cause he can sense Sora, and Dream Eaters brought joy to Sora

 

Also you are free

no more spoilers

Ventus Heart gave Sora the Armor to protect him from the Darkness.

Nightmare-Darkness possesses the Armor and but Armor still protects Sora.

Darkness-Armor sees Riku as threat and atacks.

 

And yes, Ventus smiled because he felt the same Sora did. I think the actions of Ventus' Heart should tell us "he'll be awake again", also his smiling does o:

Ven's armor was protecting Sora, then Riku came, and the armor sensed Terra within Riku, but the armor thought it was Xehanort, so it attack Riku.

 

Ven smiled because he let one rip.

and the armor sensed Terra within Riku, but the armor thought it was Xehanort.

 

That is just a theory or what, i think say that is speculate too much

Ventus armor tried to protect Sora but the armor wraped itself in darkness.

The armor protected him from darkness but then became possessed by the nightmare

Armor was protecting Sora which ended up getting possesed by the nightmare.

 

Ventus smiled cause he can sense Sora, and Dream Eaters brought joy to Sora

 

Also you are free

no more spoilers

 

Just this is confirmed,about sense Terra in Riku...it's just a theory.