The Dauthdaertya are twelve weapons created towards the end of Du Fyrn Skulblaka by the elves. They were forged using incantations, forgotten by the time of the Rider War, as well as with materials that the elves no longer remembered how to manipulate by the time of the Rider War, with the sole purpose of killing Dragons. This made the Dauthdaertya along with their wielders nearly impervious to Magic, including the magic of the dragons. The elves believed that all twelve Dauthdaertya were lost or destroyed after the pact was made between the elves and dragons. All of the Dauthdaerya were named "after the most beautiful of flowers," inciting Arya to comment on the ugly mismatch between their names and their deadly purpose. Saphira was nearly killed by a spear of this kind during the Battle of Belatona. The Dauthdaert, Niernen or "Orchid," was speculated to be the last surviving weapon of the twelve. Arya later used Niernen to kill Shruikan by burying through his eye the full length of the spear.
Niernen was a long lance/spear, with its head made in a barbed pattern that would be unusual to those used to normal human spears. Eragon observed that when its barbed blade emerged from Saphira's healed wound and "fell to the ground and bounced against the paving stones," it sounded more like pottery than metal. This particular Dauthdaert's flowery name is indicated by the stylized Liduen-Kvaedhí glyphs carved into the blade. Its barbed head was surrounded by a faint emerald glow, while the weapon itself was also of a green hue.
Note: It is possible that the Dauthdaert's abilities and the thorn-like motif on the blade was inspired by the Gae Bolg, the spear wielded by the Celtic mythological hero Cu Chulainn.