They were able to send a few scouts back and forth before they reached Arianrhod. The basic strategy was the same—take care of the Kingdom soldiers, and the mages if they join. For specifics, however, it helped to know more of the situation.
In all honesty, the mages concerned Edelgard more than the Kingdom soldiers, both by her own experience and how they seemed to react to her army moving towards the Silver Maiden. For the Kingdom's part, whatever force they had at Arianrhod seemed to be the largest they could muster, at least for the time being.
As for the mages… It did seem like their numbers were growing larger, although whether or not they would fight was still debatable. She found it hard to believe that was a coincidence, despite the mages never entering the fort or helping the Kingdom with their efforts.
She was glad she had the foresight to tell Count Bergliez to turn away any mages that tried to help defend Arianrhod when he first took position in the fort. She wouldn't put it past them to have already planted one or two mages in the ranks, but if nothing else the soldiers would know any additional ones were enemies and react accordingly.
Edelgard was fully prepared to kill the mages, whether or not they completely opposed the Imperial army—even if they helped, she knew she could identify them as the people who helped Cornelia, thus justifying any hostility. They had to focus on the Kingdom army first, but if any of the mages stayed afterwards, she wouldn't let them see another day. She decided on that immediately.
They made camp on a higher area roughly an hour away from Arianrhod, and stayed there for the night; the fort was in sight, as was the Kingdom army. The intention was to finalize any strategies and confirm everyone would be ready for a conflict in the morning. The Kingdom army could see them, she knew—and she doubted the mages were unaware either—but kept their distance.
Edelgard was up and wandering before the sun rose, despite saying the night before they wouldn't move out until an hour or so after sunrise. It was interesting to see which soldiers were awake, training or preparing or worrying, and which ones slept in a little later. She sent out another scout to confirm nothing—or nothing major—had changed overnight.
Monica opted to entertain some form of conversation with her, considering everything was decided and both had some free time. She seemed rather pleased on comment on the sunrise.
The scout returned in a lull in conversation. He offered a short bow, and Edelgard nodded to give him permission to speak.
"In terms of the Kingdom, nothing is different," the scout reported. "They seem to be preparing to face some opposition, but their formation and arrangement is the same."
"Good. And the third party?" It was easiest to refer to those who slither in the dark as merely a group who would not help them, but could hinder them.
"They've gained a few members since last evening, but still haven't moved."
Monica frowned. Edelgard didn't know if they wanted to cause chaos or just to provoke them, but she still didn't want them to go unchecked.
"Thank you for the report," Edelgard said to the scout. He gave another bow and left.
Monica looked at her before she could say anything else. "Can I do something to help?"
"See if you can gather a group to investigate," Edelgard said. "You can go with them, just be careful."
"I will. Thank you." She offered a bow and walked away as well.
Edelgard went to speak with Hubert. He scowled when he heard it, but ultimately not much of their strategy was altered—until the mages made more efforts to oppose them, they had to focus on the knownenemies. She doubted it would take more than a few hours to put the Kingdom army to rout.
She called the army together near the end of the sunrise, with Hubert standing next to her. It wouldn't hurt to move out a little earlier than initially said. She already let Monica and the few people going with her go to the mages; it would be best if the main army was close.
Edelgard began to give the order, but paused when some soldiers murmured. She looked behind her to see something in the sky—right on top of Arianrhod, coming down towards it. For a second, the strangeness caught everyone—herself included—off guard.
The whole army just watched the thing fall. As soon as she saw it hit the Silver Maiden—the sound and sight of breaking walls and fire—she completely turned.
"This…" Edelgard murmured. There were too many ways to describe it when another two or three javelins of light seemed to fall on Arianrhod.
Hubert looked at them and answered one of the possible endings. "It's very likely to be those who slither in the dark; the Kingdom doesn't have the magic for something like this nor carry through with the blatant cowardice, and Rhea would not be so kind as to give us more things to go against her."
She hated having to watch. "And we can't help those inside."
Hubert didn't respond. Her gaze followed another javelin fall from the sky and hit Arianrhod. She could see a few people leaving, or attempting to.
"…Dammit."
It only took a five or ten minutes until there was barely anything of the fort. People—soldiers and citizens, from the Empire and Kingdom—stood in a crowd outside the ruins. A few fled, or even reentered the ruins; most of them simply watched as it continued to crumble.
Edelgard waited a moment before turning back towards the army.
"We're going to search the area," she said firmly. She refused to say this was planned; she could think of a good enough excuse later. "Unless someone attacks first, don't fight anyone."
She couldn't imagine anyone would be able to fight well regardless; many of the soldiers looked unsure or frightened. She recalled the story of how Ailell was set ablaze—with believers among them, many of them likely thought of the tale as well. Claiming it was Rhea wouldn't help; to some, it would just tell them they were on the wrong side.
Edelgard led the army down to what remained of Arianrhod. None of the Kingdom soldiers fought them—after seeing that the Imperial army didn't attack, they retreated.
Monica and her group joined with the rest and gave their report: they did shortly battle the mages, but they disappeared after the javelins began falling. How…fitting of them, to slither away before Edelgard could even see them.
It frustrated her—she couldn't do anything, except to offer a place for the people who lost their homes or the soldiers who managed to survive.
The losses were great; Count Bergliez survived, fortunately, but many of his men did not. Edelgard decided it would be best to hold off on continuing the offensive in the Kingdom. She didn't want to push the soldiers, and have them leave as a result.
On her part, she needed time to accept the waste of lives.