I am looking for help remembering the name of a series of books I started sometime in the late 90s. The books themselves may have been from the late 80s. I don't remember how many total were in the series as I never finished it. I don't know why I can't remember much detail even though I seem to remember really liking them (and it really wasn't that long ago).

What I can remember:

- I think the genre was a mix of sci-fi fantasy/thriller
- The main character was a man named something like Koenig
- I believe he could talk to the dead (or at least interact with them somehow)
- He could also time travel or teleport
- I think there were vampires involved - some kind of undead, villainous threat
- Whatever they were, they lived in towers, or bred in towers, or regenerated in towers (nasty towers made of flesh or something)

That's about all I can remember. I couldn't even begin to guess at the author's name or gender. I tried hunting about on Google and Fantastic Fiction, but got nowhere. Thanks for any help!