I read the prologue and was kinda expecting a book about that - immortals versus mortal, normally aging people and the morals of killing them. The description doesn't mention that at all, and neither do the reviews I read. Is that just a prologue to shock you or is any of the later book actually about people like Tan'is?
vivek The prologue is but a small slice of the pie, this book is amazing with a intriguing plot , tons of action and amazing character buildup. Its has a few similarities with Brandon Sanderson's Mistborn trilogy. Finally , Yes there are people like Tan'is in this book.
This answer contains spoilers… (view spoiler)[It's clearly building up to that, but for this book the immortals mostly remain in the background with a few people in the foreground that we're not sure of. There is a fairly decent discussion on letting people with extraordinary powers live with regard to the leachers though (hide spoiler)]