Lol I just learned that phosphorus is incredibly rare in the universe since it can only be created by neutron stars colliding with each other, this means huge areas of galaxies would be completely devoid of phosphorus. This will make it the limiting factor in the growth of an interstellar civilization since it's absolutely vital for life, it's used to make DNA, ATP, and other basic stuff.
This might actually explain Fermi's paradox, Earth is unusual with its huge phosphorus content in the crust, which is reflected in us having a massive biosphere. Alien civilizations actually have a good reason to invade Earth, mine it out and destroy all life in order to harvest phosphorus.
https://www.youtube.com/watch?v=oPU9jeQbTOU 