These matched daggers are identical except for the stones set in their pommels. One pommel is chalcedony (opaque white), the other is obsidian (opaque black). You gain a +1 bonus to attack and damage rolls with both magic weapons. The bonus increases to +3 when you use the white dagger to attack a monstrosity, and it increases to +3 when you use the black dagger to attack an undead. When you hit a monstrosity or undead with both daggers in the same turn, that creature takes an extra 1d6 piercing damage from the second attack.