By means of this spell, the wizard changes a normal mirror into a scrying device similar to a crystal ball. The details of the use of such a scrying device are found in the DMG under the description for the crystal ball.
The mirror used must be of finely wrought and highly polished silver of a minimum cost not less than 1,000 gp. This mirror is not harmed by casting the spell, but the other material components - the eye of a hawk, an eagle, or even a roc, and nitric acid, copper, and zinc - are used up.
The following spells can be cast through a magic mirror: comprehend languages, read magic, tongues, and infravision. The fol- lowing spells have a 5% chance per level of the caster of operating correctly: detect magic, detect good or evil, and message. The base chances for the subject to detect any crystal ball-like spell is listed in the chrystal ball entry in the DMG (see the \"Miscellaneous Magic\" section).