The Apexians (also known as Venith, Angels, etc etc) are a "race" of robot-like beings that exist within the Galaxy. The Apexians were directly created by the Iraxians to serve as their successors, however, the Iraxians shrugged them aside in order to create Iraxian-based intelligent life as their successors instead. Particularly, the True Heirs.
Several different sub-types of Apexians exist, and a massive range of sizes exist for Apexians, ranging from Iraxian-sized, to the size of planets or moons. They tend to follow a type of heirarchy, but so little is known about them that it is very hard to tell. They generally do tend to be solitary, but it may be because they are capable of instantaneous communication with one another, no matter the distance.
In a way that has yet to be studied further, the Probes may be related to, or connected to Apexians. Regardless of this fact, Apexians and Iraxian-based life are technically related by the fact that they both descended from and were created by Iraxians. Despite this, Apexians do not like Iraxian-based life, and will rarely ever communicate with these civilizations. For what little communication there has been, Apexians seem to see Iraxian-based life as below them, and do not care for our affairs.