A/N: So everyone has basically accepted that Eliwood's canon wife is Ninian, who is, as we all know, half-manakete. This means that Roy is himself one-fourth manakete, and given that Kana, also being one-fourth manakete, can transform, it stands to reason that Roy should be able to as well. So I just took that and ran with it.
Kiran had recently managed to summon Ninian, and the ice manakete's first reaction to being pulled from her world was, understandably, "Where am I?" followed by, "Is Eliwood here? Is my son here?" Kiran, of course, gave the usual 'Welcome to Askr' speech, followed by saying that the two were, in fact, present. Her spirits lifted immediately in response, and, ecstatic, she cried out, "Oh, thank the gods! I couldn't bear to be separated from them!" With that, after asking where they were, she ran off in search of them. She had something important to say to Roy.
Eventually, she found Roy, who was currently walking through the castle grounds with Lilina. "Roy, it's me!" she called out to them, and overjoyed, the three got into a tight hug. "Mother! You're finally here!" Roy finally said, after releasing his grip on the other two. Lilina, too, was glad to see Ninian, "Lady Ninian! I was wondering when you'd finally arrive!" However, Ninian's expression soon turned very serious. Turning to Lilina, she ordered the young mage to head off for the time being. Lilina was understandably annoyed, and started pouting. In response, Ninian asked her a simple question: "Is that any way for a lady such as yourself to act?" Lilina groaned, shaking her head, before finally conceding and heading off somewhere else.
After Lilina had left, Roy was, understandably, concerned, and asked his mother, "What was that all about? She hasn't done anything wrong, has she?" Ninian shook her head. "No, son, that's not it at all. It has to do with me, actually." "Oh? What is it?" asked Roy, now rather intrigued by his mother's behavior. She proceeded to look him right in the eyes, and asked, "Son, has your father ever told you what I was before I married him?" Roy shook his head, a little stunned at the question. "No? Why? Is it important?" Ninian nodded. "Very. You see, I am half manakete, and thus, I can transform into a dragon. Specifically, an ice dragon. And given that you are my son…" she trailed off, but Roy understood her meaning. "...I can transform too." Ninian nodded. "Precisely. I was hoping that your father would have mentioned this at some point." Roy froze. "Actually, about that… I remember father saying he had something important to say to me when I left for Ostia. However, he was already gravely ill at that point, and, well…" Ninian was stunned by this news, and asked, "But then how is he here?" Roy shrugged. "Something to do with your soul living on for a little while after death? That's what I thought." After hearing this, out of nowhere, Ninian grabbed Roy's ear and yanked it. Hard. "OW! Mother, what're you doing!?" Ninian glared at him. "If he was here, why didn't you bother to ask him about that important piece of information!?" Roy, now very afraid, answered, "I… forgot?" This made it worse, as Ninian proceeded to slap her son clear across the cheek. "How do you forget something like that!? It's your father! You always pay attention to your father!" At this point, a few people had heard the commotion, and alerted Eliwood, who rushed over as quick as he could.
When he arrived, he shouted, "NINIAN!" Then, having successfully caught her attention, he said to her, "First of all, you have no idea how much your presence here makes me happy. Secondly, what are you doing to our son? He hasn't done anything bad, has he?" Ninian glared at him. "As a matter of fact, he has. He forgot something very important. Something you should have said to him when you first arrived." Eliwood froze. "What are you talking about- oh. That. Whoops. Would you accept 'I forgot about it' as an excuse?" In response, Ninian kneed him in the crotch, thoroughly disappointed at her husband's and her son's forgetfulness. And then she stormed off.
Eventually, Eliwood recovered, and then he stood up, looked at Roy, and said, "Well, that could've gone much better." Roy nodded. "Indeed it could've, father." However, their troubles would not end there, as Roy noticed that Lilina was rushing at them, Forblaze in hand, preparing a spell. Turning to his father, he said, "Um, not to alarm you, but I think Lilina may be attempting to murder me now." Eliwood said, "Run, son. But remember this: Hell hath no fury like a woman scorned, and right now, I think the women in our lives have been sufficiently scorned." With that, the two separated, and ran as fast as they could, and they were just in time: Where they had been standing mere moments before, was a giant, flaming crater. In response to this very real threat, something in Roy's mind clicked, and, in a motion that seemed completely natural, even though he had literally never done it before, he yanked a hidden crystal out of the hilt of the Sword of Seals. It was a fire-red stone, with swirls of icy blue embedded into it, and small flakes of snow floated around it, gravitating towards it. And then he squeezed it with all his might.
A bright flash consumed the surrounding area, and in Roy's place was a massive, blood-red dragon, with what appeared to be blue magma bubbling between the gaps in its scales. At the tips of its majestic wings burned blue flames, as did its utter behemoth of a tail. When it roared, everyone within earshot suddenly felt a burning sensation consume them, followed by an utterly freezing wind. Then it turned to face Lilina directly, snorting fiercely, and spraying snow and ash from its flaring nostrils. She froze in place, still shivering, despite how warm she was getting. Stay calm, it's just Roy… she told herself, but this did nothing to ease her nerves. She trembled as she readied Forblaze to cast another fireball, but luckily for her, she didn't have to: Eliwood, who had previously been too stunned to do anything, rushed in front of her, Durandal in hand. However, she could see he was straining himself greatly, attempting to hold back the mighty blade's urge to slaughter any dragon in the vicinity. If she could sense his thoughts, she would hear him saying, I made that mistake once with my wife. I will not let it happen to my son. But as this thought ran through his mind, Roy (in dragon form) attacked, and the wall of fire that was the brunt of his initial strike gave way to a chill the likes of which neither had felt in their entire lives, even with the fact that they lived with Ninian. But, if they could peer into Roy's mind, they would see that he was fighting as hard as he could to regain control over his dragon form's rage, and, to their surprise, succeeding. On the outside, this led to a gradual lowering of the intensity of his dragonbreath, until finally he got back full control and returned to his human form. When he got up, he looked around, and saw only devastation around him, before he laid his eyes on his father and Lilina. The two had been encased in massive ice blocks, and when he saw what he had done to them, he screamed, long and loud, and demanding that the gods punish him for all the damage he caused. But to his ever-growing despair, they did not. However, the powerful fire magic contained within Durandal and Forblaze began to melt the ice blocks, and so many had heard Roy's anguished cries, as well as the roar of his dragon form, that every available healer had rushed to the scene, staffs at the ready.
Lilina thawed out first, and just in time, too: Her admittedly delicate frame made her extremely susceptible to the cold, and it didn't help that she had been suffocating the entire time. Her skin had turned an eerie blue from the effects of both, and she crumpled to the ground. Immediately, Cecilia ordered that everyone with the ability to use Physic staffs immediately target Lilina, and she herself joined in. A few fire mages had come, too, and they immediately began to warm the area, bringing Lilina's body temperature back up to normal. But that was not enough. Everyone could still feel a biting wind around them, and the source was quickly determined: Roy. Cecilia, after realizing this, went up to Roy, and ordered that he keep his ice powers in check, or, better yet, try to use some of his fire magic to help. He did so, and suddenly the area got much, much warmer. This expedited the healing process, and it also thawed Eliwood's ice block, who was not in nearly as bad of a state as Lilina was. All the healers and mages that were not already focused on Lilina turned to Eliwood, and began his recovery as well.
Not long after Eliwood's thawing, Lilina finally woke up, and started searching for Roy. She spotted him standing a few feet away, and attempted to call him over. He rushed to her side, promising to her that everything that had transpired would never happen again. He then proceeded to hug her as tightly as was possible, but this proved too much for her, because as she attempted to return the embrace, she strained a little too much, and passed out from sheer exhaustion. However, Roy did not notice this fact right away. It was only when he pulled away and she flopped to the ground that he realized what he had done. He attempted to shake her awake, to no avail, and it was at that point that Eliwood, who had recovered by that point, came up behind him and tapped him on the shoulder and said, "There is such a thing as caring too much. Just let her rest. When she wakes up, then you can start doting on her properly." Roy nodded solemnly, and decided it was high time for Ninian to provide some proper explanation as to how to control his powers in his dragon form. He needed to know.
A/N: Yes, Roy is being an angsty teen and it is contrary to his personality but come on. It's his girlfriend. And his dad. Everyone gets scared for their loved ones, especially when you accidentally-on-purpose freeze them in person-sized ice cubes. But yeah. Sorry if anyone was OOC, because they probably were, but my logic for Ninian is that there comes a point for any parent where enough is enough. And this is enough for her. Also, #RoyisaSelfishlySelflessDork is a headcanon of mine, apparently?