Insidious Magic
( Forgotten Realms Campaign Setting, p. 36)[Metamagic]
You can use the Shadow Weave to make your spells harder for Weave users to detect. All creatures employing spells or spell-like abilities are considered to be Weave users unless they possess the Shadow Weave Magic feat.
Prerequisite
Shadow Weave Magic (FRCS) ,
Benefit
When a Weave user employs a divination spell, spell-like ability, or magic item (such as detect magic) that may detect the magical aura of one of your spells, the Weave user must make a level check (DC 11 + your caster level) to successfully detect your spells. Similarly, a Weave user attempting to use a divination such as see invisibility to reveal the effects of one of your spells must make a level check to reveal your spell's effects. The Weave user can check only once for each divination spell used, no matter how many of your spell effects are operating in an area. This benefit does not extend to spells you cast from the schools of Evocation or Transmutation. From now on, your ability to detect Weave magic is impaired.1 Any divination spell you use against a Weave effect is successful only if you make a level check against a DC of 9 + the caster's level. This penalty does not extend to Enchantment, Illusion, or Necromancy effects. (You detect them normally.)