Quicken Spell

Type of Feat: Metamagic

Prerequisite: Cast 4th-level spells, Any of the following classes: Bard, Cleric, Red Dragon Disciple, Druid, Harper Scout, Shadowdancer, Sorcerer or Wizard.

Required for: Automatic Quicken Spell

Specifics: Quickened spells can be cast instantaneously, making them invulnerable to counterspells or interruption. A quickened spell is cast as a free action, and another action can be attempted within the same round, including the casting of another spell. Only one quickened spell can be cast per round.

Use: Quickened spells occupy spell slots four levels higher than normal.

While the description says that a quickened spell is "invulnerable to counterspells and interruption", this is not the truth.

Using quicken spell does however immunize the caster against attacks of opportunity caused by casting a spell.