Rhodry, being not only half-elven but lucky enough to have lived through his battles, has reached an age where his long-lived elven heritage is beginning to show: he's still in his prime, and people are beginning to talk. Jill, now a dweomermaster in her own right, confronts him with the need to fake his own death and leave Deverry, rather than have the truth about his right to Aberwyn (or rather, lack thereof) come out. (Nevyn, having fulfilled his ancient vow, finally passed on to his next life.) The best place for Rhodry to go is to his father's people out on the grasslands, leading to Kerr's first detailed treatment of the Elcyon Lacar, known as 'elves', and fulfilling the prophecy that he would die twice.
Apart from the 'present', with Rhodry, the main thread follows Aderyn. Naturally enough, when the elven kingdoms of the far west and south were destroyed by the Hordes, driving the elves out into the grasslands, they lost nearly everything, including much of their knowledge of dweomer. Aderyn, as a human apprentice passing his final dweomer test, was given a destiny to travel west and 'make restitution'. (This picks up a thread from _The Bristling Wood_).
We finally see the beginnings of things: how Aderyn's son, Loddlaen, began to go wrong, leading much later to the events in _Daggerspell_ (and even how the ruined fortress out on the edge of the grasslands came to be there). We meet the Guardians for the first time, one of whom first got the dwarven silver ring from Rhodry's then-current incarnation, only to give it back a few generations later when it was needed.
Nevyn really wasn't lying about 'a trace of elven blood in the Maelwaedds'; upon his first return to Deverry from Bardek after Maryn's death, he travels to Cannobaen, the Maelwaedds' home, to begin creating what will later be the Great Stone of the West. (For the stone's fate, see Darkspell; for where Nevyn got the idea, follow the thread of the Time of Troubles, which begins in _The Bristling Wood_).
We also see how matters were finally resolved between Maddyn and Bellyra: not in those incarnations during the Time of Troubles, but after their rebirths and next meeting in Cannobaen. As for Rhodry's current incarnation, now that he's out on the grasslands, some incidents from past lives are beginning to crop up, and Aderyn fears he may think to ask the question nobody should ask about death unless they're ready to face the dweomer...
I was raised on C.S. Lewis's Chronicles of Narnia and later discovered for myself Tolkien's The Hobbit and The Lord of the Rings. I still remember the evening seven years ago when I opened A Time of Exile and read the prologue about the dwarven smith. I knew from the style and the tone that this was a work of some scope and that I had to decide then and there to follow the series or give this book away and forget the whole thing.
I've followed the series through and have not been disappointed. No other modern author of fantasy has had the ability to hold my attention for so long. There is a feeling of authenticity in every concept that is brought to our attention. We feel, truly, the joy and anguish of the main characters. We chortle madly with Rhodry when the berserk rage takes hold of him, and feel Lilli's despair and guilt about Maryn. And yes, we share the tedium of long sea voyages. Other authors have been flayed for less.
I am, admittedly, a very slow reader. I linger over passages and often have to put a book down to let what has transpired in the past few pages sink in. An average paperback novel will take me a few months to finish; it took me about three weeks to finish The Black Wyvern.
One can recognize that certain passages in the Deverry series are borrowed from pop culture; a scene from the movie Lawnmower Man and the Battle of Agincourt to name two. But where others might be accused of plagiarism, Ms. Kerr manages to pull it off and weaves them elegantly into her tapestry and keep us waiting hungrily for more.