Whispering Egg is a highly valuable creature egg. You can reveal its location via your Analysis Visor and they are located around abandoned buildings.
They contain multiple whispering eggs so it’s possible to make some good amounts of units by farming them. You can also find them on dead and infested planets just lying on the ground, even moons.
Larval Core is obtained once you destroy the whispering egg and you need to pick it up quickly or it disappears.
But you also need to be careful because when you do this, biological horrors will spawn and attack you immediately. And they can do a lot of damage quickly so try to jetpack away on some higher ground.
If you’re in an exocraft, they will not attack you. You can also construct building walls around the eggs or drill holes in the ground before shooting the eggs, and this will keep you safe from the monstrosities.
When all else fails, quickly jetpack to your ship and recover. 🙂