Insidious Magic (Metamagic)

You can use the Shadow Weave to make your spells harder for Weave users to detect.

(Player’s Guide to Faerûn, p. 40)

Originally posted on D&Dtools

• Prerequisite: Shadow Weave Magic,
• Benefit: Any Weave user who employs a divination spell (such as detect magic), spell-like ability, or magic item that could detect the magical aura of one of your spells must make a successful level check (DC 11 + your caster level) to succeed. Similarly, a Weave user attempting to reveal the effects of one of your spells via a divination spell (such as see invisibility) must make a caster level check to succeed. The Weave user may check only once for each divination spell used, no matter how many of your spell effects are operating in that area. All creatures employing spells or spell-like abilities are considered Weave users unless they possess the Shadow Weave Magic feat.

This benefit does not extend to spells you cast from the schools of evocation or transmutation.