Portal Through Time is an original novel based on the U.S. television series Buffy the Vampire Slayer. It was published in 2006. The author, Alice Henderson, also wrote, Night Terrors in the Stake Your Destiny series. In this novel, Buffy and her friends time-travel to four different periods of history to protect Slayers of the past from present-day vampires.
An artifact has been forged which enables time-travelling spells while it remains in Sunnydale. A group of vampire-assassins are travelling into the past in an attempt to kill previous Slayers, and disrupt the Slayer lineage. They are led by the spellcaster Lucien, whose aim is to ensure that Buffy does not interfere with the ascension of the Master. When they discover that killing Buffy in the past merely changes the way in which the Master is frustrated, they decide to go further back.
When Buffy becomes aware of their plans, the vampires have already left and she is forced to follow them into the past. With Giles, Willow and Xander, she travels to first-century Anglesey in Wales where a Druidic stronghold is being invaded by Romans. Next they travel to Uruk in ancient Sumer where they encounter Gilgamesh. Xander inadvertently arouses a plague god, and Willow accidentally summons a snake-demon while trying to banish the god.
Then they return to the American Civil War period, where they find themselves in the middle of the Battle of Shiloh. Finally they head for Paris during the French Revolution where they witness executions on the guillotine and meet Angelus and Darla.
The novel's tagline is: "Back through the chain of Slayers..."