A Darkness at Sethanon

Yes, A Darkness at Sethanon, published in 1986, is the concluding volume of Raymond E. Feist's original Riftwar Saga trilogy, following Magician (1982) and Silverthorn (1985). It resolves the overarching conflict of the Riftwar between the kingdoms of Midkemia and the alien Tsurani empire.

The novel culminates in a massive military siege at the ancient, ruined city of Sethanon, where the forces of the Kingdom confront not only the remaining Tsurani armies but also a darker supernatural threat. The battle sequences at Sethanon are among the largest-scale military set pieces in the Riftwar Saga.

The saga centers on a war between the human kingdoms of Midkemia and the Tsurani, an empire from the world of Kelewan who invade Midkemia through a magical rift. The conflict spans years and draws in elves, dwarves, magicians, and various political factions across multiple novels.

Yes, A Darkness at Sethanon is the direct continuation of events from Magician and Silverthorn, and it would be very difficult to follow without having read the first two books. Key characters, plot threads, and world-building details from the earlier novels all converge in this concluding volume.