The Karons are an imperialistic, warlike, and xenophobic species that inhabit somewhat deeper reaches of space. The Planetary Federation's member species (Species 1, the Thoroni, Soruna, V'malnons, T'larans, and I'lin) have all apparently had bad encounters with the Karons, being that no one truly knew much beyond their name and that few had ever escaped to tell the tale of such an encounter (Ad Astra 4: Sacrifice of the Angels). They are the primary antagonists of Ad Astra 4, and the captain of one Karon Bird-of-Prey is the main antagonist of Ad Astra 5: The Fight for Ferb.
As mentioned above, the Karons are an imperialistic, warlike, and xenophobic species. They are very secretive, never make permanent alliances, and are obsessed with death in honor or to regain honor. In battle, they do not care about their own lives, focusing only on furthering their goal at hand.
They show examples of this during first contact made with them by the TerraFleet vessel USS Hammurabi (PF-207) in September of 2038; they kidnap Captain Taylor Archer, and when runabouts rescue her, 4 attack ships decloak and severely cripple the Hammurabi before one suicide-rams it to finish it off, killing all 70 remaining crew members. The Karons are defeated in the First and Second Battles of H'pal, a moon nearby their main energy production facility. Nevertheless, in a later battle, the Battle of Losurae (Ad Astra 4), General Ch'nok keeps his massive prototype dreadnought (the IKS K'lathak) cloaked until he has a fabricated distress call sent so that the Phineas-A would respond, leading to an all-out battle with the Phineas-A, USS Liberty, the UIS P'lax (and I'lin vessel), and UTS Gerod (a T'laran vessel) in a nearby nebula. Not wanting to surrender even when his ship was badly crippled from a ram by the Phineas, he backs his own ship out, severely damaging both vessels, while activating his self-destruct sequence to take the Phineas with him.
Another instance demonstrating the ferocity of the Karons as warriors was when a Karon Bird-of-Prey over 5,000 lightyears away from Karon space attacked the Phineas, both ships crippling each other; Captain Phineas Flynn tricks the crew into beaming over to negotiate surrender, killing them with the self-destruct after safely beaming everyone to the planet below. In a hand-to-hand combat that ensues, Phineas fights with the Karon captain, leading to his dangling from a cliff. Phineas offers him a hand, the captain instead grabbing Phineas' leg in the effort to take him with him to his doom below; Phineas kicks him off and then takes the captured Karon vessel back through the spatial rift to a V'malnon medical base in Federation space with the unconscious body of Ferb.