I imagine once the events of Trespasser are over and the Inquisition has disbanded at least publicly, the first order of business for Zevran and Revka is a long, LONG vacation. Zevran - while able to act anonymously through proxies and correspondence - can't leave the Crows unattended indefinitely, or he risks upstarts attempting to hijack his title of Shadow Prince of the order. And he did promise to bring Revka to Antiva, after all.
So the two travel to Antiva City for a year or so - Zevran managing his responsibilities and the odd attempt to suss out his identity/assassinate him while making time to show off his beloved home. And Revka, for the first time in possibly her life, gets to relax for a time.
But she has responsibilities back in Fereldan as well, and her's are not as easily managed from afar. With things in order in Antiva they travel back to Amaranthine, Revka's return to her role as Warden Commander not easy, but manageable. The pair fall into a routine of traveling back and forth between their two homes for varying lengths of time, and have a sense of precious normalcy.
There's investigations into the Calling going on throughout this, of course, but it brings only minor leads and less than promising results. Which is fine, for a time. Until during one of their stays in Antiva, when things begin to seem a bit... Off.
The sunlight always used to bring a vibrant glow to Revka, but now no amount of it can drive off the grey pallor settling in around her eyes. She tires faster, sleeps more poorly than ever before, and a faint cloudiness begins to make reading without spectacles difficult. And the nail in the coffin comes in the middle of the night after a month of things growing slowly worse, when Zevran wakes to find Revka's side of the bed empty.
He finds her huddled in the lounge, curled up in a corner with her knees drawn as tightly to her chest as possible. And she's muttering to herself in some garbled language, partially in common but broken up by words that don't sound like words at all, only gutteral noise.
They leave the next day, back to Fereldan indefinitely. And on the way back to Amaranthine, they make a long overdue visit to a run down tower and leave with a third in tow. After all, Avernus was only allowed to live because of them.