A unicorn horn is used to make a herblore ingredient that can be obtained as a drop from unicorns and black unicorns. It can be ground down to unicorn horn dust using a pestle and mortar. The dust can then be used as an ingredient in antipoison, super antipoison and sanfew serum potions. It is also used alongside a cowhide to summon a Unicow in the Tower of Life.
- There are five unicorns that spawn in Kourend Woodland, south of the Woodcutting Guild. All five of the unicorns guarantee a drop of 1 unicorn horn.
- The Fremennik Province east of Rellekka, north of Swaying tree at the rare tree icon. With fairy ring access AJR this spot is not far from a bank, and there is very little competition. There's 6 unicorns in total, but only 2 of these unicorns drop unicorn horns. (The other 4 are black unicorn foals.)
- You can receive a Unicorn horn from Barbarian Assault by using the Gamble option when selecting rewards.
- There are two unicorns that roam the area between the Barbarian Village and Edgeville. The Edgeville bank is nearby, and the area is easily accessible.
- By using fairy rings to Ardougne Zoo (fairy ring code BIS) you are sent to a cage containing 2 unicorns.
- Levels 15-21 Wilderness, found east of Graveyard of Shadows, there are around 10 black unicorns. This can be a good source if you don't mind the risk associated with the wilderness and the level 101 ents nearby.
- After completing Tower of Life, players can mix 1 cowhide with 1 unicorn horn on the northwest altar in the Tower of Life basement to spawn an unicow that can drop from 2 to 4 unicorn horns, typical strategy involves bringing 1 horn and 10-12 cowhides to get a full inventory.(If you have Easy Ardougne Diaries some of the Unicorn horns will be noted. When you have medium they will be almost all noted. So you need to bring around 10-12 Cowhides and 10-12 Unicorn horns.)
- There are two unicorns that roam the area just northwest of Catherby. The Catherby bank is nearby, and the area is easily accessible.
- One can be found roaming around the camping adventurers, between Lumbridge and Draynor Village.
- Two can be found south of the mine southeast of Varrock.
- One can be found northwest of the Hosidius farming patch in Great Kourend, using the Xeric's Glade teleport on the Xeric's talisman.
For an exhaustive list of all known sources for this item, see here