SRD:Lyre of Building
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Lyre of Building: If the proper chords are struck, a single use of this lyre negates any attacks made against all inanimate construction (walls, roof, floor, and so on) within 300 feet. This includes the effects of a horn of blasting, a disintegrate spell, or an attack from a ram or similar siege weapon. The lyre can be used in this way once per day, with the protection lasting for 30 minutes.
The lyre is also useful with respect to building. Once a week its strings can be strummed so as to produce chords that magically construct buildings, mines, tunnels, ditches, or whatever. The effect produced in but 30 minutes of playing is equal to the work of 100 humans laboring for three days. Each hour after the first, a character playing the lyre must make a DC 18 Perform (string instruments) check. If it fails, she must stop and cannot play the lyre again for this purpose until a week has passed.