That was certainly a mysterious dream. I'm sure that the different elements will be explained later. It's no wonder Gavin had become so quiet after returning. That was almost as scary for Lisa watching the beating as it was for Gavin.

Looking at the symbolism in the dream, I think there is a reason that Gavin and Marina were walking like robots. Its because they weren't Gavin and Marina, but just representations of them. I have a feeling that Raikou is the one putting the memories of Gavin's torture into Lisa's dream.

Her eyes were still not right; they were golden in colour, but they suddenly held a goldmine of knowledge.

She swiped the gold sceptre at the tapestry; the yellow jewel on the end glowed as it tore the tapestry in two to reveal an old passageway.
Raikou was probably taking the form of Marina to get Lisa to follow. Lisa also had a sapphire sceptor, shich probably symbolizes her connection with Suicune.

I wonder, maybe the Key and Ebony Box are what the man was talking about when he was beating Gavin.

That may have been a short chapter, but it definitely gave some things to think about. I wonder what Gavin's reaction would be if Lisa told him about the dream?