D&Dtools

You create a disk of magical energy 10 feet in diameter and 2 feet thick.
The disk is incorporeal and invisible when first created.
Whenever a spell is cast or a spell-like ability is used within the 10-foot diameter of the spell engine, it activates, absorbs the magical energy, and begins to glow and spin, providing light as a torch.
The spell engine similarly absorbs most spell effects targeted at it.
It absorbs all these effects as if it were a rod of absorption with an unlimited capacity.
Over time (1 hour per spell level absorbed) the engine slows to a stop and becomes dim and translucent, but it remains capable of absorbing magical energy indefinitely.
If an activated spell engine comes in contact with any permanent (noncharged or single-use) magic item, it destroys the item and explodes for 1d6 points of force damage per caster level (maximum 20d6) to all creatures in range, destroying itself in the process.
Magic already in place when the spell engine is created (such as a glyph of warding) or carried into its area (such as an invisibility spell on a creature) are not absorbed unless they are somehow directed against the spell engine (such as an antimagic field pressed against it).
A spell engine absorbs any dispel magic spell directed at it.
A detect magic spell cast outside the spell engine's range detects it normally.
A disintegrate spell causes the spell engine to explode as if it had contacted a magic item.
Preparing spells within the light provided by a spell engine takes only half as long as normal.
Material Components: A disk of polished bone, one of your tears, and a silver wheel worth 1,000 gp.
XP Cost: 250 XP.