You can cast a spell without it being visible that you do so.
Prerequisite: Spellcaster level 9, school of Illusion is not a forbidden school.
Alternate Prerequisite: Level 7 Illusionist.
Benefit: When casting a spell, a glamer effect is used so that it cannot be seen or heard that you are doing so, preventing attacks of opportunity and counterspelling. The effects can still be seen, so not with all spells can it be hidden that it was you who cast it. A hidden spell takes a slot 3 levels higher than normal. If it is also stilled and silenced, this lowers to 2 slots for a total of 4 slots higher.