Steven Freeman discovers the Necronomicon in the Voorhees house

The Necronomicon Ex-Mortis is the Book of the Dead. It originally appeared in the Evil Dead series, but has appeared in the Friday the 13th timeline.

The Necronomicon was found by Steven Freeman in the Voorhees house implying that it may have been this book that gave Jason his power.

In the comic series Freddy vs. Jason vs. Ash, Freddy Krueger used the Necronomicon to resurrect himself and later to increase his power so he could use it in the real world.Though, Caroline used it to open a portal leading to the Deadite Dimension, in which the Necronomicon and Freddy were sucked into it, however the Necronomicon reappeared.