a cornerstone

Object 'oddly shaped rock cornerstone' is type armor, material rock.
Extra flags: nonmetal nolocate.
Weight is 5, value is 3, level is 50.
Armor class is 4 pierce, 5 bash, 6 slash, and 6 vs. magic.
Affects movegain by 5.
Affects luck by 1.
Affects con by 2.
Affects hitgain by 10.
Affects managain by 10.
Affects ac by -10.
Rare item.