After activating the Vault on Havarl, look for two Nexus Scientists at the south end of Pelaav Station, discussing a giant adhi.
They need help scanning wildlife being rewritten by the monoliths, and you're just a scanner-wristed passerby to do it.
Start by checking the database inside the base. It'll give three targets to pursue- a challyrion, rylkor, and eiroch.
The closest target is the challyrion- just north, near the astronomer's house from Forgotten Stars. Only it turns out not be one Challyrion, but a pack.
Still, you're in a pack too. Take them down, then scan a specimen.
There's also a container in the cave they were occupying.
Next up are the rylkor, withing spitting distance of the Forward Station in the middle of the map.
Another pack- kill them with fire, scan a corpse, then head to the south end of the Ancient Courtyard for your eiroch sample.
The mutated eiroch looks a lot like an Ancient Eiroch, and packs the same punch. When you get there, he's distracted by massacring Roekaar, but they won't last long. Take him down with fire and lots of dodging- if he gets his claws on you it's nearly always game over (though teammates he savages can be revived normally). Luckily, this eiroch doesn't dissolve on death, so you can wait 'til it's down before scanning. Your new objective is to scout the supplies the Roekaar had with them. There's a few lootable containers, a mineral cache, and scannable core, but the questmover is a datapad which reveals their nefarious plans, and a camp location.
Head to the far north to find this camp in the Remnant ruins there. It's guarded by adhi, raiders, and sharpshooters, so spend a little time winnowing them down from a distance before charging in.
When they're finally dead, access their data at the research station.
You have the choice to save this genocidic data or delete it entirely. The choice has no effect in this game, so make your call, loot the camps, then return to the Nexus Scientists at Pelaav Station. Relay your data and your choice, One of the scientists will be more pleased with your choice than the other, but either way they'll get to work, leaving you with a Viability point reward.