Currently there are two special events, the Assimilant Incursion and the Scorpion Nest.
Both have a 5% chance to spawn everyday 5 days after the last event of its type has occurred.
Resistance = voltage / current.
"We are the Assimilants. Resistance = voltage / current." - Typical example of Drone humour.
The Assimilant Mothership will appear somewhere, and begin collecting Nebula Gas. When it has reached a certain quota it will construct an Assimilant Hive. While the Hive lives it will produce Assimilant Drones and Assimilant Fighters so long as it has a supply of nebula gas. The drones help gather additional nebula gas while the fighters move around engaging both Players and NPCs. If they manage to strip every nebula tile in a sector down to 0 they will then move onto the next sector continuing until they have been completely destroyed.
The Scorpion Fighter is
"The Scorpion Fighter is"- Professor Baldur, famous arachnophile.
A Scorpion Nest will appear in pass sectors, and will spawn Scorpion Fighters.