The old arts tell of an occult process of fermenting a cockatrice egg in basilisk dung for 100 nights. The poison in the artifact is perfect in its fatal potential (if thrown on a living target roll fortitude [DC 30] or die, success causes 5d10. Repeat for 1d4 rounds.)
The Egg is as fragile as a mundane egg, and smells of dead river clay.
The purpose of the egg is not as a weapon however, and was original meant as a focus for forgotten ritual spells (remnants of which may remain, or have been meaningless fragments without the Egg for reference). It modifies the effect of traditional spell casting in its vicinity. Healing spells may cause disease (15%) within 50 yards of Poison Incarnate. Curses have the same chance to be permanent. Investigation may find other peculiarities. Anything wet or damp within 10 miles of the Egg will spontaneously generate files, mosquitoes, frogs, snakes, and spiders. Each will be the deadliest mundane variety. Brown recluse spiders, odd emerald green arrow poison frogs, black mambas, the smaller insects carry malaria and other disease and are eaten by the frogs, which concentrate and intensify the harmful substances over time, wicking it out of their skin.