This is the scene where Ash and Serena will begin the power of the heart jewel and the final battle between the heroes and villains begins in Ash and Serena's Great Adventure.
(Later Ash and Serena made it to the giant door)
Ash Ketchum: Are you ready for this?
Serena: Yes.
Ash Ketchum: Just stay close to me.
(Ash and Serena opens the door as we see Xehanort sitting on his throne chair)
Xehanort: At last, those two heroic lovers arrive. Please... come in. Such determination to get here... It seems that you manage to get to my castle
Ash Ketchum: Yes, but you're not gonna get with this!
Pikachu: Pika!
Xehanort: Do you think so? Hmm... we'll get to that.
Serena: So what's next?
Xehanort: Well since your friends are busy fighting my army, you two and you're Pokémon will face me.
Ash Ketchum: That's right, Xehanort!
Serena: Besides, I do not let evil forces win!
Xehanort: Oh, I think you do. But perhaps you need a little nudge.
(The darkness appears out of Xehanort's hand possessing Serena)
Ash Ketchum: Serena!
Xehanort: (Laughs)
(Then Serena becomes Dark Serena)
Ash Ketchum: Serena! No!
Pikachu: (Worried) Pika!
Xehanort: Yen Sid should have warned you... You are alone, my boy, and your Pikachu. You two have always been alone. Still, here you are... trying so desperately to save this miserable world... refusing to accept the true role of becoming a Pokémon Master. I'm sure you've been told that I was the first of my kind but I assure you, there have been many. It has been the duty of our predecessors to bring back Kingdom Hearts... to bring about the great cleansing. This is the true nature of our kind. Your destiny is to destroy this world.
(Ash and Pikachu are thrown into the wall)
Ash Ketchum: (In Spyro's voice) No! I don't believe that! Serena!
Pikachu: (Angry) Pika!
Xehanort: Of course, you don't. But you have fulfilled your destiny nonetheless. In my time I was prevented from completing my quest. But you... you and your love have carried the powers of the heart jewel... be it through your own will or not. And soon, the world will become eternal darkness using the powers of the heart jewel, then you will be destroyed along with your friends and your Pokémon teams.
Ash Ketchum: No!
(Dark Serena hits Ash)
Dark Serena: Fight back!
Ash Ketchum: Serena, please stop! I can't fight you back!
Pikachu: Pika!
Xehanort: (Laughs evilly)
Ash Ketchum: Serena, please! You got to remember!
Dark Serena: Fight back! Why won't you fight back?!
Ash Ketchum: Because your my girlfriend, and Xehanort had nothing to fight for!
(Then light appears out of Ash's right hand as he touches Dark Serena's right hand making the light turn her back to normal)
Serena: What happened?
Ash Ketchum: Serena! You were possessed by Xehanort's dark powers turning you into a heartless. But now I turn you back to normal.
Serena: (Hugs Ash, crying) Oh, Ash, thank you! I thought I was going to be a heartless forever!
Ash Ketchum: It's okay, just be happy I turn you back to normal.
Serena: I love you.
Xehanort: Argh! So be it! You've made your choice and so you shall meet your suffer! Prepare to die!
(Xehanort created the dark battlefield as Ash throws his Pokeballs summoning Greninja, Hawlucha, Noivern, and Talonflame. Serena throws her Pokeballs summoning Braixen, Pancham, and Sylveon as the final battle begins)
Xehanort: Let's see how you deal with my army of mega-evolved Pokémon!
(Xehanort brings out Garchomp, Tyranitar, Aggron, Gyarados, Salamence, Banette, Steelix, Scizor, Glalie, Houndoom, Aerodactyl, Pinsir, Heracross, Sharpedo and Absol)
Xehanort: Now, Mega Evolve together!
(Xehanort unleashes dark powers to mega evolve his Pokémon army into Mega Evolutions)
Ash Ketchum: This ends now, Master Xehanort.
Serena: Yeah, it's time to finish this.
Xehanort: I'll be finished! When the powers of the Heart Jewel belong to me, then the Keyblade War will be continued! And you two Lovers and you're friends will be dead! Get them!
(Xehanort's Mega Evolution Pokémon army charges toward Ash, Serena, and their Pokémon)
Ash Ketchum: Pikachu, thunderbolt! Hawlucha, Karate Chop!
Serena: Braixen, use flamethrower! Sylveon use fairy wind!
(Pikachu fires thunderbolt at Mega Gyarados, Hawlucha uses Karate Chop at Mega Tyranitar, Braixen fires flamethrower fires flamethrower at Mega Heracross and Pinsir and Sylveon fires fairy wind at Mega Salamence)
Xehanort: Use Hyper Beam!
(Mega Tyranitar, Aggron, Salamence, Gyarados, Houndoom, Heracross, Pinsir, Absol, Garchomp, and Banette fire Hyper Beam all together towards Ash, Serena and their Pokemon. Back at the battlefield down below our heroes are continuing to fight the villains and they hear the explosion that's coming from the floating battlefield where Ash, Serena, and their Pokémon are fighting Xehanort and his Mega Evolution Pokémon army)
Tino Tonitini: Oh, no!
Max Taylor: Ash!
Zoe Drake: Serena!
Tai Kamiya: We've got to help them, or they'll be toasted!
WarGreymon: Then we must help them!
(They fly to help out but the Villains block their paths as the other heroes fight the Villains)
Sora Takenouchi: Go, help out Ash and Serena! We'll hold them off!
Tai Kamiya: Okay!
(They fly up to help Ash and Serena out. Back at the floating battlefield, as the smoke clears Ash, Serena along with their Pokémon are badly wounded by the massive hyper beam attack)
Ash Ketchum: Serena! (He tries to run to her but his leg was totally injured) I can't get up!
Serena: Ash! Help me!
(Xehanort walks to Ash and Serena)
Xehanort: You are finished two lovers.
Serena: No, we won't!
Xehanort: I'm afraid so! Now perish!
(Garchomp, Tyranitar, Aggron, Gyarados, Salamence, Banette, Steelix, Scizor, Glalie, Houndoom, Aerodactyl, Pinsir, Heracross, Sharpedo and Absol in their Mega forms roar)
Xehanort: Garchomp, Aggron, Heracross, Gyarados, Salamence, Steelix, Aerodactyl, Absol, and Pinsir, Stone Edge! Go!
(Mega Garchomp, Mega Tyranitar, Mega Heracross, Mega Gyarados, Mega Salamence, Mega Steelix, Mega Aerodactyl, Mega Absol, Mega Aggron, and Mega Pinsir fire Stone Edge towards Ash, Serena and their Pokémon and they got directly hit)
Ash Ketchum: Ouch! That smarts!
Xehanort: Heh heh heh heh! Now Absol, Glalie and Houndoom, Dark Pulse!
(Mega Houndoom, Mega Absol, and Mega Glalie fire Dark Pulse towards Ash, Serena, and their Pokémon, and they get directly struck)
Serena: What power!
Xehanort: Next, Will-o-Wisp! Go for it, Houndoom and Banette!
(Mega Houndoom and Mega Banette fire Will-o-Wisp toward Ash, Serena, and their Pokémon and they feel the burn)
Xehanort: Hah hah hah hah hah!
(Ash and Serena and their Pokémon team scream in agony due to the burning from Will-o-Wisp)
Xehanort: Say goodbye, fools! Absol, Pinsir and Scizor, X-Scissor!
(Mega Pinsir, Mega Absol, and Mega Scizor cross their arms and fire X-Scissor on Ash and Serena and their Pokémon crew)
Xehanort: (in Hunter Boss's voice) WE'RE FINISHING THIS ONCE AND FOR ALL, AND WE'RE DOING IT WITH CRUNCH! USE IT NOW!
(Mega Tyranitar, Mega Garchomp, Mega Salamence, Mega Steelix, Mega Gyarados, Mega Aerodactyl, and Mega Sharpedo use Crunch and bite Ash, Serena, and their Pokémon army)
(Serena, Ash, and their Pokémon scream in pain as they try to shake off Mega Tyranitar, Mega Gyarados, Mega Aerodactyl, and Mega Sharpedo)
Serena: Their jaws won't let go of us! Somebody help us!
Xehanort: Ha ha ha ha! Looks like I've won! Dragon claw!
(Mega Garchomp, Mega Tyranitar, Mega Aggron, Mega Salamence, and Mega Aerodactyl use Dragon Claw on Ash and Serena's Pokémon)
Xehanort: All right, use Flash Cannon!
(Mega Aggron and Mega Scizor fire Flash Cannon on Ash and Serena's Team)