To craft Diablos Armor and Weapons you need to find Majestic Horns, Twisted Horns and Spiral Horns. Finding these materials in Monster Hunter World requires you to hunt Diablos in the Wildspire Waste and break both its horns.
This will reward you with the Majestic Horn most of the time. Diablos can usually be found in zone 15 in the Wilspire Waste. Make sure to check the world map if he is there before you run to the zone. In case he is not there travel to different maps, each travel will change up the monsters in the maps.
HOW TO BREAK THE HORNS
One of the quickest ways to farm for these horns is to bring a hammer and some flashpods (location shown in the video 00:30).Blind the diablos first and then smash his horns with a few hits. The hammer is the perfect tool for this task because you only need to land a few shots on the head to break the horns.
After that you can instantly leave the expedition and claim your rewards.
HOW TO GET MAJESTIC HORNS
Normal Diablos will drop Majestic Horns if you break both horns
HOW TO GET TWISTED HORNS & SPIRAL HORNS
Both of these horns are a possible drop from breaking both horns from the black diablos.
CRAFTING & ITEM LOCATIONS
ALL PALICO GADGETS
MONSTER & TRACK LOCATIONS