The Obscura are a hostile race introduced in The Last Federation: Betrayed Hope as part of the invasion game mode.
The Obscura are a particle based lifeform which, in Invasion Mode, enters the solar system at the same time the Acutians and the Evucks wipe out the Hydrals. In this case, when the protagonist crash lands on one of the remaining planets, the Obscura follow them and wipe out the local population. The protagonist narrowly escapes in a prototype spacecraft and races off to warn the other races of the danger and convince them to partake in a counterattack. The Obscura are shown to be much tougher then the average species with advanced ships and ground forces which usually require armadas to wear down and destroy.
In Standard Mode, the Obscura remain present, but as a scattered nuisance rather then a grave threat. They control multiple hideouts which the player will sometimes be asked to attack to find cures for various diseases. The Last Federation