Spell engine

Spell engine was an arcane abjuration or alteration spell that created a magical device that absorbed virtually all spells cast in the surrounding area and produced a light that was conducive to magical study.

Effects
There were at least three slightly different versions of this spell. The newer version was wholly in the abjuration school while the older versions belonged to both the abjuration and alteration schools. This spell took a full ten minutes to cast and produced an invisible and intangible disk: the spell engine. The older versions placed the 12 ft (3.7 m) diameter disk at the point where the caster stood at the time of casting, while the newer version produced a 10 ft (3.0 m) diameter disk that could be placed up to 65 ft (20 m) away (even farther for more experienced casters). For all versions, the disk was 2 ft (60 cm) thick. The effect was permanent until dispelled or destroyed.

Before the spell engine was activated, its presence could be detected by detect magic or detect invisible spells (if cast outside the spell engine's area of effect) or by the equivalent natural abilities. Once activated, the disk became visible but remained insubstantial.

With few exceptions, any divine or arcane spell, any spell-like ability, or any magic item discharged within the area of effect would activate the spell engine and be absorbed, as if by a rod of absorption with unlimited capacity, causing the disk to turn and give off a white glowing light. All further magical casting in the area was prevented from having its desired effect as the energies were siphoned into the spinning disk instead. The older versions of spell engine protected a spherical volume with a radius of 10 ft (3.0 m) per level of the caster, ignored barriers such as walls and solid objects, and the disk spun faster and glowed brighter with each absorbed spell. The newer version covered only the physical dimensions of the disk itself, spun at a constant rate, and glowed like a torch.

The glow given off by the spinning disk was beneficial to spellcasters. Studying or praying in the light of the spell engine allowed them to memorize spells in half the normal time. The amount of rest needed to recover was not affected, only the time to prepare spells.