The Verenian Watchers
Arrows of Dragon-Slaying
Arrows of Dragon-Slaying are magical ammunition made specifically to magically harm dragons. These arrows belong to a specific class of magic item known as arrows of slaying, which are all enchanted with a very powerful magic that is attuned to a specific beast. The nature of the enchantment makes it very difficult and very expensive to create these arrows, and thus they are extremely rare and highly coveted.
Unfortunately, the enchantment is volatile, and over the course of centuries, the effectiveness of the magic is lost. If the arrow is not used within five hundred years, the damage the arrow causes the creatures it was made to slay becomes much less potent.
Katariah Lavelathorn has a few expired Arrows of Dragon-Slaying.
A regular arrow of slaying causes creatures of the type it’s attuned to to make a DC 17 Constitution saving throw or take 6d10 necrotic damage. After the arrow has hit a creautre it has attuned to, it loses all magic.
If the arrow goes for five hundred years without being used as it was intended to, the effect changes. An expired arrow instead does an additional 3 necrotic damage, without forcing the creature to make a saving throw.