For two hundred years he has been imprisoned within a comet, brooding. For two hundred years he has had nothing to do but think about the unfairness of it all, and to hate the Continuum for putting him here, and to hate her for driving him to it.
When he made the decision to save his mortal lover's people from the Borg, he didn't think there would be any serious consequences. Technically, it's forbidden to intercede at that level, particularly against the Borg, but other Q break that rule all the time and nothing really bad ever happens to them. And her people are prized by many in the Continuum as confidants, listening boards. It is impossible to safely expose one's true emotions to other Q, and particularly impossible to ask for emotional advice without risking being mocked for the next ten thousand years over it. He isn't the only Q to find value in talking to an El-Aurian Listener, and not the first one to enter an emotional relationship with one.
So when he saw the Borg on their way, he came up with what he'd thought was a particularly clever plan. He put a forcefield around the El-Aurians' solar system that would block out all subspace communication, thus instantly breaking the connection Borg had with one another. It meant that the El-Aurians needed to use regular lightspeed radio to communicate within their own solar system and relay stations at the edges to convert between subspace and lightspeed radio, but that was a small price to pay for salvation from genocide, he thought. As soon as a Borg cube crossed the forcefield, all the Borg within would lose their connection, not only to the Collective, but to each other. Then the confused, partially amnesiac, lonely creatures would be vulnerable to El-Aurian emotional manipulation, promising them friendship, connection and understanding to replace the Collective togetherness they had lost. By the time the Borg adapted to the forcefield, the El-Aurians would have taken in a few thousand former Borg, who would bring with them Borg technologies. El-Aurians were a peaceful people, never having needed more than their skills at managing other sentient beings to avoid conflict. That technique wouldn't work on the Collective, but the technologies brought by former Borg would. It was elegant and it would hoist the Collective on its own petard. He's still proud of it, even after what it's brought him.
He didn't stop to think about why none of the other Q who had El-Aurian friends or lovers had bothered to come up with a solution. He was egotistical enough to assume it was just because they weren't as smart as he was, or didn't care as much as he did. It never occurred to him that his difficulty with politics back home, and his lack of desire to follow it, could hurt him.
Because what he didn't know was that some high up in the Continuum fear the El-Aurians, precisely because of the emotional hold they have on many Q. The Continuum only works as a unity because its members need to turn to one another for emotional connection, and if the Continuum stops working, none of them will be able to channel their powers. The destruction of the El-Aurians wasn't planned by the Q Continuum, but in the eyes of some of their most influential Q it was greatly to be desired. And the method of his interference put together beings who presented a psychological danger to the Continuum's existence with beings whose drive toward perfection and adaptability made them a future potential physical threat. The Continuum was not amused.
So they threw the book at him. He was shocked, totally uncomprehending, when they sentenced him to ten thousand years imprisoned in an asteroid. Although the Q can move through time, the way such an imprisonment works will prevent him from later returning and moving freely through the universe during any time that he has been in his prison. El-Aurians are long-lived by mortal standards, but in ten thousand years his lover, and her children, and her children's children, will all have long ago become dust. And he raged, and protested the unfairness, but none of it mattered. He saved a species the Continuum wanted dead, and created an alliance between two peoples the Continuum greatly feared an alliance between. He placed his mortal lover above the needs of his own kind. They called him a traitor and they locked him away.
And so he who cannot bear any length of boredom has been doomed to near-sensory deprivation for two hundred years, nothing to see, nothing to hear, nothing to do but brood on the unfairness of his sentence. He hates the Continuum for doing this to him, and he hates his mortal lover for being his weakness, for luring him into disobeying the Continuum for her sake. The joy she once gave him curdles with rage, and he begins plotting revenge against her. Not that he'll actually be able to do anything to her directly, because she'll be long, long dead once he is released. But he'll find a way. He'll torment her great-great grandchildren, or he'll revoke the protection he once gave her people from the Borg, or he'll destroy them himself.
The time drags on with no marker and no respite, and subjectively seems eternities longer than it actually is, but his objective, Q sense of time needs no markers. He knows he's only two hundred years into what was supposed to be a ten-thousand year sentence when the asteroid shifts around him and the force field that binds him here weakens, energy from the outside intruding through it. In a moment he sees the chance for freedom, and takes it, following the energy path to its source.
And she is there.
Astonished, he materializes, finding himself aboard a spacegoing vessel. There are several El-Aurians manning various consoles, and his lover in the middle of the room, already running toward him. "Oh, thank the holy! It worked!" She throws her arms around him. "I'm so sorry it took me this long to find you. I've been searching ever since I found out what they did to you."
It has never, ever occurred to him that a mortal, any mortal, even the one he sacrificed his freedom to save, would search for him or seek to free him. Honestly, he wouldn't have thought a mortal capable of freeing him, but even besides that, it never occurred to him that she would try. All the resentment and rage he built up toward her in his captivity melts away in a moment. "How... did you find out?"
"I have my ways," she says, smiling. "Some of your kind are almost respectable, you know. Not everyone agreed with what your Continuum did to you, or why."
"And they told you where I was?"
"'Where' in a relative sense, yes. I've been searching for you for almost two centuries." She shakes her head. "I can't believe they did this to you for saving us."
"I can't believe you went looking for me."
She smiles brilliantly at him. "Did you doubt it? You saved my people. And even if that hadn't happened, I told you. I love you. I would never abandon you."
There will be consequences, he knows. The Continuum will come and try to take him back. He may have to literally fight for his freedom. He may have to go into hiding, or find as many friends and supporters as he can to back him in an appeal. But for now it doesn't matter. He holds her tightly against him, marveling at the sheer simple joy of being material, of being able to feel. For now, he is free.