Diamond Sword (5e Equipment)
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Martial Melee Weapons
A longsword edged with blue diamonds. Blue diamonds are less brittle than clear diamonds, but still make for an unreliable edge. Still, some warriors seek such a blade for their superiority at cutting through metal armor.
When you make an attack with a diamond sword, and the attack die shows a 1 or 20, some of the blue diamonds forming the blade's edge break. The first time this happens, the weapon's armor piercing property is reduced to +1. On the second occurance, the weapon loses its armor piercing property. On the third occurance, the weapon becomes an improvised weapon that deals 1d8 bludgeoning damage.