Straight from the steam update page

Overview Reconnect to your last match! Balance changes Crash Fixes Social Menu fixes Miscellaneous fixes

Helldivers, the Omens of Tyranny have arrived! The Illuminate are back, and with them, a new wave of terror threatens our democracy. After nearly a century of relative peace, these technologically advanced enemies have returned. The Illuminate are conducting mysterious invasions across the galaxy, seizing our colonies and converting our citizens. These staging attacks and Illuminate disappearances are too precise and elusive to suggest a full-scale planetary conquest, but their methods and intentions remain a dire enigma.

A new faction Missing for almost a century, the Illuminate will challenge our recruits more than the other factions they have faced. They are advanced, highly-intelligent beings wielding powerful technology that appears to average citizens like a kind of dark magic.

The Illuminate have seemingly emerged from the singularity created by the destruction of Meridia. Even though we don’t know the true origin of the invasion, we have no choice now but to suppress three factions in the Galactic War.

New colony missions Omens of Tyranny is bringing the fight into the streets, with new mission areas inside Super Earth’s many colonies.

But it won’t be easy. Gone are the wide open spaces that Helldivers are accustomed to fighting in. Cities mean closer quarters, dark alleys, and forked paths where one wrong turn means meeting a horde of Voteless to liberate.

New FRV vehicle With all these new developments, there won’t be time to take driver’s ed. courses, Helldiver. A Fast Recon Vehicle “FRV” will now appear in the colonies, ready to plow through the Illuminate at high speed.