Dragonbane bolt

Dragonbane bolts are bolts made to kill dragons, requiring 60 Ranged to wield. When used against dragons, these bolts deal 40% more damage with auto-attacks and 25% more damage with abilities, and they gain a flat 30% accuracy bonus.

Dragonbane bolts are not obtainable until completion of the Ritual of the Mahjarrat grandmaster quest and are untradeable, although assistable.

Dragonbane bolts do NOT work on skeletal wyverns. Ava's device will retrieve these bolts.

During a slayer task of dragons, wearing a full slayer helmet, pernix armour, a royal crossbow and praying Anguish while overloaded, one can hit over 900 in legacy mode with dragonbane bolts which is 9,000 in EoC.

Making the bolts
77 Mining is needed to mine the bane ore, which is located in the Glacor Cave, in a side cave near the exit to the ritual site, protected by an energy barrier. The quickest way to reach the cave is by using the fairy ring. 87 Magic is then needed to use the Tune Bane Ore lunar spell on an item from a dragon, such as dragon bones or dragonhide in your inventory. This will turn only 5 of the ore in your inventory into dragonbane ore per cast.

Then 77 Smithing is needed to smelt the ore into dragonbane bars at a furnace. There's a furnace in Zanaris, but any furnace could be used. Then use the fairy rings to go to Kethsi, using then. Use the Kethsian anvil on the upper level to make 50 unfinished bolts per bar, which requires 82 Smithing. Adding feathers at this point turns them into finished dragonbane bolts, with 80 Fletching.

The Magic, Smithing, and Fletching requirements can be boosted or assisted. Therefore, using spicy stews and an extreme magic potion, the lowest levels possible to obtain these bolts are 76 Mining (required to complete the quest), 80 Magic, 77 Smithing and 75 Fletching.

Trivia

 * Currently, the bolts do no additional damage to the dragons in the dungeon of a player-owned house. It is unknown whether this is a bug.
 * Even though the in-game skill guide states that 80 Smithing is required to make these bolts, the required level is actually 82.