Second Chances (Dark-Hunter, #7.5)
Originally included in the Dark-Hunter Collectible Booklet and Dark Hunter Companion.
This is the short story that was given away with Unleash the Night about Acheron and his brother Styxx.
It can be found in Acheron and Dark Bites.
You can also find it for free in its entirety at the link below and clicking "Read Book Excerpt".