Mega Events are an optional type of Random event
Dread Lords event
Dread Lords start to colonize a planet using their advanced technology. Try to attack their planet before they have a chance to construct powerful ships. Your ships will automatically start moving towards the Dread Lords planet.
Note: Like with the Peacekeepers, it is possible to contact and trade technologies with the Dread Lords when they are a Mega Event, however this is by luck. Depending on your Diplomic stat and Relationship factors, they may be very willing to trade tech for credits, or not. One method of contacting them is when they make peace with a Civilization, Major or Minor. [Single case: More info needed] - Gigaus
Strange ships suddenly jump into the galaxy apparently to keep the peace through any means necessary. See Peacekeeper Strategy for help on this potentially painful event.
A mysterious and deadly plague appears in the galaxy, severely reducing population growth(?) and threatening to destroy the major civilizations of the galaxy. Once this event occurs, the technology "Plague Cure" becomes available for research, with the only pre-requisite being Xeno Medicine. Plague cure is the only way to reverse the plague's effect (the Yor require Antivirus Technology instead).
Precursor Artifact Event
A certain race comes across a Precursor artifact that boosts their civilization dramatically.
Over time the race becomes more and more powerful, if the civilization is left alone they will very difficult to deal with in the later stages of the game.
Pirate Fleet Event
Similar to the Peacekeepers Event, except their fleets appear throughout the entire map and they will attack any ship not belonging to them. This could ruin your game entirely unless you possess a formiddable starfleet.
Jagged Knife Event
Planets from their respective civilizations break away and become the Jagged Knife.