The Lava Core is the fourth and final map in the Story mode as of version 1.02. It generally looks like a underground-like alien habitat. It seems like as if it was a place for mining but the lava has probably risen to the mines so now the mine is now flooded with lava and swarmed with Aliens. There seem to be mithril here which attracted the aliens to make it their home.
There is also a mysterious tall figure in the background if you look closely, it is unknown what the mysterious tall figure is but it seems like to be teasing a new boss in the feature or it is just a alien overlord in the background that may not be added in the future however it is mostly speculated.
The lava core is also home to the Cerberlisk boss, which is a tall and evasive alien overlord found in stage 4-6. The lava core also introduces two new aliens: The Mambull and the Demster Just like every other stage the lava core has 6 stages but the difficulty in the lava core has risen to a greater amount. Every type of alien appears in this stage so be cautious when you are fighting a swarm of them.