Arrow of slaying

An arrow of slaying is a magical arrow that is intended to do a massive amount of damage to a specific type of creature.

Appearance
The arrow of dragon slaying that Vex found in the ice in Rimefang's lair was dark green, and the arrow shaft was rough and metallic.

Properties
An arrow of slaying is a one-use magical item. If a creature of the type it is intended to slay is hit by it and takes damage, they must also make a Constitution saving throw of DC 17 or else take an additional 6d10 piercing damage. They take half damage on a success. Once the arrow has dealt the extra damage to the intended creature type, it ceases to be magical, though can still be used as a standard arrow.

Arrows can be of varying specificity; there are both dragon slaying arrows and arrows specifically intended for a certain type of dragon (eg: red dragons). There are also bolts of slaying for use in crossbows.

History
After the Slayer's Take trial to kill Rimefang, Vex noticed an arrow in a frozen quiver in the lair that seemed to have not been damaged by the ice. She pulled it out, and Lyra identified it as an arrow of dragon slaying.

Zahra later crafted an additional arrow of dragon slaying, which she gave to Vex and told her to use it in her fights against the dragons of the Chroma Conclave.

Vex used one arrow in the attack on Umbrasyl, which hit. She thanked Zahra for it not long after, and asked if she could make another one, which Zahra did. Vex shot one arrow towards Thordak, which missed and was lost. Later in the same battle, she shot her final arrow, which hit, and which did the damage necessary to destroy Thordak's soul anchor gem and reduce him to normal ancient dragon size.