Praetor Lemnos is a powerbroker who used his power of erasing himself from others memories to build himself a strong powerbase. He assembled the army Terror Firma to assist him in his goal of creating a new order in the universe and started a war that cost many lives. He is also responsible for the destruction of several worlds including Orando and reduced the brilliant Coluans to gibbering idiots. He was stopped by the Legion, who now holds him in custody.

Terror Firma is an army of super powered mercenaries hired by Lemnos to bring about his new order. They were later folded into the group called the Wanderers. » SEE: Wanderers: Earth-Prime

The Dominators are an alien race that has come into conflict with Earth for centuries.  No one is sure what they are currently plotting but they seem to be tied to the appearance of Supergirl in the 31st century.

The A.I. Electrolords once conquered the Earth before being banished. Recently, there seems to be alot of robot insurgency and attempts to ressurect the A.I. Electrolords. What this means for the Legion only time will tell.