The PC version of Monster Hunter: World is still a bit behind the console versions, but as Capcom announced today, a free update coming tomorrow will help catch us up. Along with a medley of bug fixes, the update will add a new monster: Deviljho, a hulking brute of a wyvern known for its size and appetite.
Deviljho comes with two sets of high-rank armor and a stylish suite of weapons, many of which are quite strong despite their negative affinity (more on that here). Defeating Deviljho will also unlock the Dragonproof Mantle which reduces incoming dragon damage, prevents the dragonblight debuff, and increases the dragon damage your weapons deal.
To unlock Deviljho, download the update and reach hunter rank 12 (you don't have to finish the story, just the quest that unlocks Pink Rathian), then look for an expedition with an unknown monster in the area. If you don't see one, load into an area and check the map again. Once you find a wild Deviljho, you can either collect its tracks or hunt it outright.
Either way, once you encounter a Deviljho in the wild, return to the research center in Astera and speak to the scholars there. They'll tell you to collect more info on Deviljho, which translates to researching it the same way you did Pink Rathian. Once you fill the research bar, you'll get the special quest "The Food Chain Dominator."
Deviljho can invade high-rank quests and expeditions just like Bazelgeuse, so you'll be seeing a lot of him. If you want to farm his weapons or armor, you can replay his optional quest or collect investigations by hunting him in expeditions. I recommend the latter, since his gem can be tough to get and investigation drops improve your odds of getting rare items.
You can find more on the update, including the full list of bug fixes, in this Steam forum post.
