The Barrier of Naath-Tith
The Barrier of Naath-Tith is a fictional incantation which first appeared in Brian Lumley's Dylath-Leen. It features heavily in another of his short stories The Horror at Oakdeene.
The Barrier of Naath-Tith (also known as the Wall of Naach-Tith or Naath-Tith's Barrier) is a powerful formula which may be used to create a barrier to build an invisible forcefield of great strength. As well as being used to create protective fields the barrier can also be used as a temporary means of imprisoning an entity. It has even proven capable of holding a Great Old One captive on several occasions. Casters should be careful lest the Barrier prove a prison as well as a safeguard.
I have been unable to find more than the first few words of the formula used to create this barrier. The words are as follows
Lethiktros Themiel, phitrithte klep-thos -From the Cthäat Aquadingen - remaining text is corrupt and illegible.
This formula is often employed by the summoners of Yibb-Tstll to protect those within from the god's possible displeasure. For this reason the Barrier is referred to as Soul Sealing in a number of magical texts (the English Book of Eibon mistranslates this as Soul Searing).
The words required to raise the barrier are relatively obscure and may prove hard for the enterprising sorcerer. The Latin translation of the Cthaat Aquadingen mentions the spell but only in passing. Most copies of the Liber Ivonis contain the correct formula though it is missing from the English Translation.
The spell may also be found in Chapter Ten of the Unaussprechlichen Kulten
Create Barrier of Naath-Tith provides magical and physical defense. Costs 1D10 san and a variable number of mp of one or multiple casters. Each magic point spent adds 1D6 points of Str. It takes 1 minute to cast and the barrier lasts 1D4+4 hours. Anyone who knows the spell can participate. Projectiles can pass through the barrier if it's damage is higher than the Str. People inside the barrier can escape by overcoming the Str of the barrier. They can't combine their Str.