Othercide

This is story related and cannot be missed. After you complete the tutorial and are taught about how to use your Inner Void to spawn Daughters and whatnot you’ll be prompted to go on a mission to close a Synapse Node. On the first day you only have one Node option so simply select your 3 Daughters and go in (you don’t have to use the Daughters the game prompts you to use, I used two Soulslingers for example).

The first mission is a Hunt mission, basically kill everything, at the top of the screen you can see how many enemies are left to kill.

After you do that your Daughters warp back to you, the Synapse is closed, and your achievement pops.