Towards the latter part of the game, when the story really gets going, you’ll start to encounter beings called Starborn. They will be rare enemies that crop up at various points throughout the story. Every time you kill one, instead of getting loot, you’ll absorb something that’s called Quantum Essence.

There are a finite number of these Starborn in Starfield, so you’ll definitely have to go out of your way for this one. If you just stick to the story, you will fall short.

Thankfully, every time you visit and complete one of the game’s temples, you’ll have a Starborn to face off with after you leave the temple. I completed 11 temples by the time I went to do the last two missions (see One Giant Leap (50G)) and I unlocked this achievement during the penultimate mission, “Revelations” (I ended up with 22 in the end). There were more temples for me to seek out as well - 15, according to my stats - so there's not a shortage of them per se, you just really need to seek them out.

So, in order to get this, you’re going to need to visit Vlad regularly for the side mission, “Power from Beyond,” to get temple locations. Then, simply visit the temple locations that Vlad gives you, defeat the Starborn Guardian at the end (outside the temple) and you’ll have 20 Quantum Essence in no time whatsoever.

Incidentally, you can check how many Quantum Essences you’ve collected if you go to the pause menu and then go up to “Powers.” At the bottom of the Powers screen it will say “Use Quantum Essence” and then a number in brackets. Provided you’ve not used Quantum Essence to increase your Starborn power regeneration speed for 60 seconds, then that number will be how many you’ve collected so far.

Once that number reaches 20, this achievement will unlock.