Sword of Truth (the first book) has a tyrannical lord of a kingdom whose greatest crime is killing anyone that can challenge him, but not a Sauron style of dark lord. I couldn’t get past the first few books.
The second book in my Archon Saga has a true dark lord. Here is an excerpt from the prologue that sets the conflict.
Archons gathered in a large, empty void within the cosmic realm, a similarly remote pocket of the Astral Plane. They didn’t wish to be disturbed. From their vibrant radiances, she realized they were archons of tremendous power – each of them as mighty as her. For a while, they waited without purpose and circled the emptiness. Then the space before them seemed to ripple. Lights began to flicker and solidify into mana of various colors. The violet mana of despair and sadness came first. Then the green mana of envy took form. The red mana of wrath and hatred, much like her own power, came next. Finally, pure black mana shadowed them all – the mana of death itself.
At first, she believed the others brought some great embodiment of archonic power into being, but she realized her error. A single entity amassed in the center of the gathering. A tremendous archon, swirling with all the colors of the dire archons, emerged from the light. It was terrifying to behold, yet utterly captivating. It dwarfed the others in both size and magnificence.
They flickered with reverence for their master. Nearly two dozen archons, who were gods in their own right, paid homage to this eternal grim idol.
“Go!” the supreme dire archon bade them. “Prepare for my coming.”
As one, they flew away, as swiftly as they had come, in an eerily stunning outburst of streaking lights, reds and greens and violets and even a few stark black. As they retreated, they began to wink away, falling from the Astral Plane – to Earth. It was then Amber noted their countenance.
They were all archons of overwhelming radiance, and they were all dire archons, filled with rage, envy, greed, despair, hatred, and pure dread. Every one of them.
In the third book, his true intentions are revealed, and he becomes human, but for the second book, yup, he’s pretty much a dark lord that represents all evil and terrorizes the protagonists. It also happens to have Irkalla, the Babylonian Goddess of the Dead, as its main antagonist.