Well, that sure made you wonder where things are going! Its NOT a volcano, and Lance and Darius aren't in any grave danger? I guess all the fire, lava, earthquakes and noises could be created by some enormously powerful pokemon, though I have no idea what kind. Maybe they were going down to fight whatever was creating the disturbance?

Lisa's parents were there, and her Dad was one of the strongest trainers in the middle of the cave fighting off the Union members? This makes me wonder if they aren't just pokemon researchers. Could that be a cover for them actually being part of the Anti-Union group?

Wasn't Entei killed in one of the earler chapters? If so, then he couldn't be the cause of the eruption, unless the legend involves the resurrection of a legendary?

You had mentioned that Gavin's Psychic powers had returned. Right now, we don't know where he is, but I hope he knows that his powers are back. That could come in handy if he was taken away with the Union leaders before the attack started. (I wouldn't think the leaders like Sterling would stay around to fight. They would run and hide while the grunts get attacked.)

There were a few grammer problems in there somewhere, but that is understandable in a 9,878 word chapter. The fact that it always had you on edge as the events unfolded kept it from feeling long.

The way the chapter ended, with the mountain's violence subsiding, and the Union being defeated, it looks like Lisa is going to finally have a chance to sit down and have a talk with someone to learn what is actually going on. I hope you don't have any trouble writing the next chapter, as I'll be looking forward to having some of these mysteries cleared up.