After almost four years of digging, theorizing and discussing discoveries, the GTA Online community has finally cracked the so-called Mount Chiliad Mystery, and the result is... rather disappointing, actually.
The culmination of all the conspiracy theories and extremely far-out concepts is a single, short, not particularly interesting mission involving the same aliens as the ones Michael encounters during a drug-induced hallucinatory trip.
The mission was first discovered by data miners and although there is also a way to legitimately trigger the mission through proper gameplay, the requirements don't exactly seem worth it. You'll have to put in a lot of effort, and more importantly, time, into unlocking this easter egg, and it might end up feeling anticlimactic.
Basically, you'll need to run 601 Gunrunning sell missions. Yes, 601. That's a lot of sell missions, and no one will hit that number for several weeks, if not months, legitimately. Some players place the average time for a sell mission to be 5-10 minutes. Even counting with 5, that makes over 50 hours.
The payoff for all that work and effort? If you pull off 601 sell missions and then initiate a supply mission at some point between 21:00 and 23:00 (in-game time, mind), a new kind of supply mission will trigger. You'll be tasked with stealing alien eggs from a downed UFO, which is logically guarded by armed aliens who aren't too hot on the idea of you using their unhatched offspring to fuel your criminal activities.
After popping half a dozen E.T.s, you take home the eggs and the mission is over. That's it. It will never trigger again - this is a one-time affair - and that's the last you'll hear of these off-world visitors who, when you think about it, were likely just a family on space-road-trip who, I don't know, ran out of gas or something, and you stole their kids and murdered them. You asshole.
Moral implications notwithstanding, it's understandable that the people who invested copious amounts of time and effort into solving the Mount Chiliad Mystery - named as such for a mural found on said mountain depicting clues to the aliens - might find this to be a letdown. All that work for naught but a reskinned supply mission? That has to sting.
There is, however, much about the Mount Chiliad Mystery that suggests more may be on the way, and that players were wasting their efforts until now. As proven in the past by the bigfoot mystery, the payoff of which was only added in a later update, these mysteries simply cannot be solved up until Rockstar adds the solution through a patch.
Thing is, there is no telling how official this even is. For all we know, this could be one "rogue" developer hiding these tidbits in the game, allowed to do so by his or her superiors simply because it doesn't detract from the actual work. If some enthusiastic developer is doing this in their free time, it would explain why the progress is added with patches, and why this payoff was so small.
That said, the very fact that these solutions were added progressively means that there very well might be more additions on the way, in order to deepen the mystery of Mount Chilliad. The mural which started all of this has an icon that looks a lot like a jetpack, which is something the mystery hunters were hoping to be the ultimate payoff for all their hunting - and this may yet come to pass.
In the meantime, if you're hell bent on some cross-species violence, get ready to grind some gunrunning sell missions, because you'll be at it long.