Keys to the Demon Prison by Brandon Mull

He reveals that Nagi Luna was the one who orchestrated Seth's receival of the artifacts. Graulas grows strong and takes the Translocater and the Sands from Seth. Seth escapes to Fablehaven and uses the Sands to heal Graulas.

A mysterious figure gives Seth a sack containing the Translocater and the Sands of Sanctity. They plan on a rescue mission, however they are captured by the Sphinx, thus giving the society 4 artifacts. Meanwhile, in Fablehaven, Vanessa reveals her secret, Grandpa and Grandma Larsen are alive and they are undercover spies for the Knights of Dawn. Bracken is stuck in human form due to him giving up his horn to make the Font of Immortality. He takes Seth to Nagi Luna, a demoness who aids the Sphinx (but secretly wishes to betray him and open Zzyzx on her terms) Seth befriends Bracken, a unicorn with no horn. He also tells Seth that he is a shadow charmer and has the Font of Immortality, the last artifact. The Sphinx reveals that they are in Living Mirage the fifth secret preserve, and he is the caretaker. Meanwhile, Seth is summoned to talk with the Sphinx. Trask, Tanu, and Kendra escape with the Translocator. After a series of trials they get the artifact, only for the society to capture them. Several members of the Society appear and the group quickly flees to the Obsidian Vault where the Translocator is hidden. Laura quickly kills Camira and reveals that many members of the Society are waiting to ambush them. They are welcomed by the caretaker Laura and the twins Camira and Berrigan. They go to Obsidian Waste, the preserve in Australia. Graulas asks Seth to recover the Sands of Sanctity so he can die peacefully. Kendra, Seth, and the Knights of the Dawn continue to take the last possible steps to safeguard the keys and locks placed on Zzyzx. In this explosive series finale, allegiances will be confirmed and secrets revealed as the forces of light and darkness collide in a desperate, climactic battle to control the keys to the demon prison. In an effort to intercept the final artifacts, Kendra, Seth and the Knights of the Dawn race to strange and exotic preserves across the globe. If the legendary prison is opened, a tide of evil is certain to usurp control of the world. After centuries of plotting, the Sphinx - leader of the Society of the Evening Star - is after the final artifacts- the Chronometer and the Translocator -needed to open the great demon prison, Zzyzx.

Keys to the Demon Prison by Brandon Mull