''Threshold'' is a fantasy novel written by Sara Douglass in 1997.

The story concerns a glassworker slave named Tirzah, forced into slavery because of her father's debts. She's tasked with helping building the eponymous Threshold, a pyramid made partially with huge glass panels. She meets a Magus named Boaz, hiding behind a Magi exterior a little too well. The Magi base a religion and magic power around the One, the number of all creation. And Threshold is being built to allow them to tap into the power of Creation and [[AGodAmI become immortal]].

Once Threshold is completed, though, it... doesn't go quite as planned.

!!Provides Examples Of:

* AntiHero: Boaz.
* BadPowersBadPeople: All of the Magi.
* DeathByChildbirth: [[spoiler:Neuf]]
* ExtraOreDinary: Being an Elemental lets you speak to glass and metal.
* GoneHorriblyRight: Threshold lets the Magi tap into the Vale... only it [[spoiler:summons a demon that starts [[TakenForGranite turning everything to stone]].]]
* HeelFaceTurn: [[spoiler:Boaz, after he finally starts to see just how evil Threshold has become.]]
* InfantImmortality: Averted. One of the first things Tirzah sees after arriving in Gesholme is a newborn baby having its head splattered against a wall.
* {{Jerkass}}: Magus Boaz, Chad-Nezzar.
* MagicalGesture: The swirling colors required to [[spoiler:speak to the Soulenai]].
* OffscreenMomentOfAwesome: [[spoiler: Boaz enters Threshold entirely on his own, and we never get to see him fight Nzame.]]
* {{Precursors}}: Soulenai.
* RapeAndRevenge: [[spoiler:Yaqob stabs Boaz in the stomach for the things he did to Tirzah.]] Also RevengeBeforeReason.
* SecretArt: Elementals and Cartomancers.
* YouCannotGraspTheTrueForm: The Vale, when Tirzah and the others look into it.