Eirika's group was surrounded by the forces of Grado! 

They had no choice but to flee into the desert! 

Riev: Valter... You should stop playing around. If you don't' finish off Eirika's forces swiftly... Her brother's left the capital. He should be arriving here shortly. You don't want to be fighting her still when he arrives. Trust me. We are equals here in Grado's army. Would you like me to assist?

Valter: All you need to do is vanish, you disgusting old man. Eirika is mine. I won't let you have her. She is so strong, so beautiful... She's the prey I've dreamed of.

Riev: Heh heh heh... Your fangs are still sharp, eh? Good. Very good. Ah, Valter... You're a beast. You're bound to no country. You care nothing for friend or foe. Kill a man, claim a woman... You live for nothing more, you wretched beast. That's your strength. That's what makes you stronger than any many alive. A beast acts without remorse. Man's morality cannot win. It's nature's way... The stage is all yours, Valter. Do not fail to get the girl's bracelet. Our master demands it...

Riev then teleports off to leave Valter to his duty. 

At the same time... 

You and Ephraim's group reached Jehanna Hall, which was in ruins. 

(Y/N): Well, looks like this place is ruined. 

Duessel: Two of the strongest of the Empire's generals, Valter the Moonstone and Caellach the Tiger Eye are here. 

(Y/N): In that case,  let's take them out! 

Lyon teleported over to Caellach. 

Lyon: How goes it, Caellach?

Caellach: Ah, Prince Lyon. Thank you, Your Highness, for gracing me with...your royal...er...

Lyon: You can stop. There's no need for you to put on airs. You were made general for your military prowess, not your flowery speech.

Caellach: And an honor it is. You know, Prince Lyon, you've got a lot of nerve. You're really worked over your dear friend the princess of Renais. Are you satisfied?Lyon: Is there some reason you ask?

Caellach: No, not really. I just wanted to see how you'd react. That's all.

Lyon: She... Eirika has always been a very important person in my life. Both she and her brother have been friends of mine for a long time. Tell me, Caellach, do you have any friends to speak of?

Caellach: Huh? Yeah, I got one. An old mercenary I fought with, went by the name of Joshua. He was a fool and a scoundrel, but now that he's gone, I miss the lad. I don't know where he's at or what he's doing, but...Lyon: Do you miss that life? Do you ever want to be a mercenary again, to see him?

Caellach: Nope. The time we worked together was fun and all, but... No. I don't want to end up another no-name mercenary lying dead in a ditch. I'd rather serve the Grado Empire and make a name for myself. I'm going to see how far my axe will take me. And then, one day...

Lyon: One day, you'll kill me and be emperor in my stead. Is that it?

Caellach: Uh... That's...

Lyon: It's all right. Think whatever you like if it helps you do your duty. As long as you do what I assign you to do, I'm happy. But for now, I'm going. You know what you need to do.

Caellach: Yep, leave it to me. I am General Caellach, the Tiger Eye of the Grado Imperial Army, after all! Once my prey is within my reach, I never let it escape. Too bad for the princess, but they've no chance of winning. None at all.

Both of your groups start taking down all of the members of Caellach and Valter's armies, and soon- 

(Y/N): GIRLS! 

Eirika, Ruby, Weiss, Blake, and Yang: (Y/N)! 

They all hugged you, and then Eirika hugged her brother!

Ephraim: Eirika! Are you alright? 

Eirika: Yes, I'm fine Brother! Wait, is that really you? 

Ephraim: Yeah, it's really me. 

Eirika: Heh, even when we were children, you were always there to protect me. 

(Y/N): Guys, we got company! 

Caellach and Valter appeared! 

Caellach: Now the crown will be mine! 

Valter: Don't hold back a single second! 

You and Ephraim fought Caellach, while Team RWBY and Eirika fought Valter! 

And it ended in satisfaction! 

Ruby cut off the head of Valter's wyvern, leaving him to fight on the ground, and then Eirika had stabbed him in the face, while Weiss, Blake, and Yang stabbed him in the body! 

You and Ephraim sliced Caellach in half as he mutered out how he was so close to getting the crown! 

And soon... 

(Y/N): Looks like you guys have gathered a bunch of allies. 

Eirika: So have you. 

L'Arachel: Greetings, I am L'Arachel of Rausten, the pleasure is mine of course. 

Ruby: Hey, I remember you! We met you before we headed out to the mountains! 

Weiss: What happened to Vigarde? 

(Y/N): We took him down. But the war isn't over. 

Innes: Is that so? 

Ephiraim: However, something remains that still bothers me. A Grado man named Knoll told me about something called a "Dark Stone." Their mages had uncovered lore that led to them to craft a powerful magic stone. This Dark Stone may have been the catalyst of Grado's transformation. It seems to be the source of that black wave of energy Myrrh described. Vigarde died some time ago, but the power of the stone played him like a puppet. The war and everything that passed since was planned by the Dark Stone's master.

Innes: Well? Who is it?

Ephraim: ...I still can't believe it, but I'll tell you nonetheless. According to Knoll, the man behind this is Lyon, the imperial prince. He said Lyon's got the Dark Stone.

Blake: Wait, isn't he your old friend? 

(Y/N): Exactly! 

Eirika: That doesn't make any sense. Ephiraim and I know Lyon better than that. We've been friends for years. Lyon's not the sort of person who could start a war like this.

Innes: But, Eirika...

Eirika: I saw Lyon recently. Ephiraim, you might know this, but after I abandoned the sea route to Rausten, I travelled overland with Prince Innes to Jehanna. We ran into trouble with Grado's forces, and I chanced upon Lyon. He didn't share his details of the situation, but he intimated that he was on our side. Despite all appearances, he was on our side. So Lyon...

(Y/N): The thing is Eirika, we met Lyon, and he was different. 

Ephraim: Yes, he didn't seem to be human. This is what he told me: He said he was behind this war. He said he'd befriended us solely so that, one day, he could invade Renais... He told me he killed our father. I know. I can't believe it either. I refuse to believe it. How could he have planned all this since he was a child... I simply can't fathom it. I've heard Lyon changed when he acquired the Dark Stone. I've no interest in magic, but... There was something uncanny about him. It seemed almost as though he were being controlled by something himself.

Yang: What does it matter? We got to kick his ass anyway! 

(Y/N): Exactly! 

L'Arachel: Wait, there is something that needs to be done first. 

(Y/N): What is it L'Arachel? 

L'Arachel: I do believe you felt it as well. The Dark Stone held by Prince Lyon... It exudes a malefic miasma. We might be able to handle Prince Lyon alone, but that stone is beyond our ken. 

Ruby: So? 

L'Arachel: We've all heard the legend of the five Sacred Stones. They alone possess the power to seal the demon king away forever. So, of course, to dispel demonic magic, we must use the Sacred Stones!

Innes: You expect us to pin the outcome of this war on some fool legend?

Ephiraim: ...Not just the legend. We also have hope. According to Lyon, he has already seen the destruction of Grado's, Frelia's and Jehanna's stones.

Eirika: Hm. That explains something... Grado forces attacked me, intent of destroying the Stone of Renais. If that's the reason they chose to invade Renais... The power of the Sacred Stones may be greater that we'd ever known.

L'Arachel: Yes, exactly! If we acquire a Sacred Stone, we'll be able to oppose the Dark Stone's might!Innes: But three of the stones have been shattered, and our options are few. Do you suppose that, during the invasion of Renais...

Ephraim: No, I don't think so. The Stone of Renais is hidden by the power of Eirika's and my bracelets.Eirika: Grado has made many attempts to take our bracelets. Everyone has failed, and so the stone may still be safe.

Ephraim: We have to confirm that, of course. We've defeated Grado, and we must turn our eyes to our homeland. It's time to return to Renais.

Team (Y/N): Right!