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 (alternatively one could complete Hero's welcome, but it would not matter because tune bane ore is only accessable after a certain part of Ritual of the Mahjarrat) and are untradeable, although assistable.

Dragonbane bolts do not work on skeletal wyverns, as they are not classified as dragons. 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 or 9,000 in EoC with dragonbane bolts.

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 all the ore in your inventory into dragonbane ore at once. The dragon item used will not be lost.

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 either use the fairy rings to go to Kethsi, using then  or go through the World Gate. 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.

Effectiveness
In terms of damage, Dragonbane bolts are less effective than ascension bolts, however they are more effective than royal bolts. This is because Ascension ammunition provides 864 damage while with the extra 25% applied to abilities the dragonbane ammunition only provides 720 damage. This means that, if accuracy is not an issue, ascension bolts are superior. However, due to the inherently high accuracy of ascension crossbows, players should find that ascension bolts would be better, if only slightly so. In addition, ascension bolts are less time-consuming to acquire.

In comparison to royal bolts, it is more favourable toward the dragonbane bolts. While royal bolts do slightly more damage, the lesser accuracy of tier 80 weapons makes the accuracy bonus of dragonbane bolts more useful.

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. Level 80 is required for bane arrows.