Blade of Despair and Hope
This +5 keen longsword is made of adamantine with a mithril pommel. When bathed for 8 hours in continuous sunlight (only natural sunlight will do; magical effects such as the daylight spell are not sufficient), it gains the holy special quality as well. If the sword is instead bathed for 8 hours in continuous moonlight, it gains the unholy special quality. While the blade is considered holy, allowing direct moonlight to touch the blade immediately dispels the holy quality. Similarly, if the blade is imbued with the unholy quality, direct sunlight will dispel it.