Last Legionary

A series of Young Adult books by the author Douglas Hill, the Last Legionary consisted of four main books as well as a prequel novel called, appropriately enough, Young Legionary.

The series had the main character Keill Randor returning to his homeworld, only to find that due to enemy action, he has become the only survivor with his homeworld destroyed. Saved from a lingering death by a secret organisation and accompanied by a telepathic alien, Keill sets out to track down and destroy an evil organisation hell-bent on conquering the galaxy.

Galactic Warlord covers Keill returning to Moros and narrowly avoiding being killed along with everyone else, due to damage sustained in a brief spacefight. He vows to avenge his people and sets out to find out who committed the atrocity and whether there are any other survivors, which brings him into contact with the Overseers and Glr and also, a group of thugs masquerading as Legion survivors.

Deathwing Over Veynaa sees him set out on his first mission on behalf of Talis and the Overseers; to a civil war between asteroid miners and the Veynaan government. Agents of the Warlord, the Deathwing, are seeking to escalate the conflict and gain control over the valuable substance mined in the Veynaan asteroid belt.

Day Of The Starwind has Randor investigate reports of mercenaries whose skills seem equal to the Legion's, taking him to the desolate world of Rilyn; where a rogue planetoid regularly brings massive storms known as the Starwind to its surface. There he finds the Deathwing at work once again; working to try and produce their own Legion; with clones of some of Moros' greatest warriors.

Planet Of The Warlord was the final book in the quartet, and finally revealed the nature and homeworld of the sinister Warlord. Keill competes in the Battle Rites of Banthei in order to draw attention to himself and his enemies out of the shadows. It works all too well and Keill is captured. Can Glr rescue him from the clutches of the Deathwing before he reveals the location of the hidden Overseer base?

Tropes used in Last Legionary include:

Absent Aliens: Although there are a wide variety of humanoid forms; they're all genetically human, just mutated by the effects of their respective environments; high-gravity worlds get shorter, heavier humans and so on. The only genuine alien is Glr, and her species isn't from the same galaxy.
Armour Is Useless: Averted. Both Lord Th'run's natural armour, and The One's exoskeleton prove to be incredibly difficult for Keill to get through.
Ax Crazy - Several of the bad guys are in it because they love to kill.
Badass - The main character: last of a famously tough group of mercenaries, known throughout the galaxy as highly-skilled, thoroughly-trained badasses. Trained practically from birth to survive on a Death World and kill or incapacitate other people with his bare hands or whatever comes to them.
- Badass Abnormal: Keill was already a Badass before he got his metal bones implanted.
- Badass Army - The Legions of Moros. Nuked by the Big Bad because they are so scary.
Brainwashed and Crazy: Arachnis briefly does this to Keill.
Combat Tentacles - Arachnis uses these both to restrain its victims and to mind-control them
Death World - Moros. It's how the Legionaries got so good at fighting, everything on their planet was out to kill them.
Determinator: Keill Randor; his planet has been saturated with life-destroying radiation, everyone he ever knew or loved is dead and he himself is dying slowly from the dosage he received in high orbit. Still, mustn't let that get in the way of finding out who did this and showing him just why it was a bad idea, right?
Distress Call: When Moros is attacked, all of the Legionaries who're away on missions or whatever are summoned back by Central Command. Once Command realised what was happening, they set up a warning beacon to try and keep those who were arrived later from trying to land.
Doomed Hometown - The Big Bad turns the Legionaries home planet into a radioactive wasteland in order to stop them from deducing his existance and coming after him. One got away...
The Dragon: The One is this to the Warlord, who is totally immobile.
Evil Cripple: The One can barely walk without his exoskeleton, and has to drag himself along on tentacle-like legs.
Evil Genius: The Warlord seems to have a few working for them. Quern is the one responsible for developing the bizarre new radiation weapon that was used to kill off the population of Moros and the whole industry of Golvic appears to be devoted to engineering ingenious armour for Altern. Golvician scientists also created Arachnis.
Exposition of Immortality: In Galactic Warlord, Talis patiently explains to Keill that the alien Glr is not an "it" but a she, and that the Ehrlil are very long-lived, the scientist who first encountered her was his father. Flr herself chips in that she's four hundred, and still considered a wayward youth by her people.
Faster-Than-Light Travel: Overlight - a hyperdrive that allows a ship to travel the vast distances of space at huge speeds; cutting cross-galactic travel to a matter of days and weeks and interstellar to hours and days. Intergalactic travel still takes a long time though.
Genocide Backfire: The Big Bad deciding the Legions of Moros were the major obstacle to him conquering the galaxy and that eliminating was the best course of action? Doesn't work out so well. The Legions weren't even aware of the Warlord's existence prior to the attack that left Keill the only survivor of his race.
Gladiator Games - Keill participates in one to draw out the enemies by attracting their attention
Hired Guns: The Legions of Moros were mercenaries, after all. Mercenaries with standards, but still mercenaries.
Hive Mind - the Warlord is comprised of 24 mindlinked humans connected to a supercomputer
Hyperspace Is a Scary Place: Previous human efforts to use Overlight to travel to other galaxies have lead to failure, the expeditions disappearing or coming back driven insane from the prolonged exposure to the endless nothing.
Implacable Man - Keill Randor. Vengeance does this to a man.
Instant Sedation - Specialised dart-guns that carry a powerful soporific chemical.
The Juggernaut: The One when he's in his armoured suit.
Kung Shui: "Demolition!" - In Young Legionary this is both a means of practicing hand-to-hand combat techniques and letting off steam for the Morosians; rooms set up with various hard objects to smash. It's often used as a means of racing between two legionaries.
Last of His Kind - Keill Randor. His strike group happened to be the furthest away when the recall order was given
Last Starfighter: The Last Legionary. Hey, all of his friends were killed by the Villain in a sneak attack, too!
Little Green Man in a Can - Altern is a mutated human with a small body and limbs which are tiny and almost non-functional. He relies on his golden exosuit for mobility.
Made of Indestructium: Keill's skeleton, after the Overseers have replaced his irradiated bones.
One-Man Army: Keill Randor again.
Prequel - Young Legionary. Describes how Keill, and every other Legion member, became such a Badass.
Proud Warrior Race Guy - Keill Randor. What did you expect?
Psychic Block Defense - Glr uses telepathic mental shields so alien that human telepaths cannot detect them, or the minds behind the shields.
Psychic Radar: Glr uses this in Galactic Warlord to detect the presence of an unspecified number of human minds in Thr'un's base on Creffa and again in Deathwing over Veynaa. The human telepath encountered in Deathwing can also use this, though his range is much smaller than Glr's.
Roaring Rampage of Revenge - Keill smashes multiple enemy groups in his quest, but he most invokes the Roaring part during the final battle in Planet Of The Warlord.
Starfish Aliens - Glr, who's essentially a telepathic space bat. And a child by the standards of her people at only 400 years old.
Starter Villain - Lord Th'run of Irruq-hoa, who leads the Warlord's advance fleet.
Super Strength - The One when he is wearing his golden armour as above
Unlucky Childhood Friend - Oni Wolda who dies of radiation poisoning but manages to warn Keill in time for him to escape alive
Void Between the Worlds: It's where Overlight takes ships; described as a non-place, a seperate void of nothingness where things and the laws of physics cease to exist.
We Help the Helpless: The Legions of Moros were often this. Mercenaries they may have been, but the Legion code precluded fighting for oppressors and those who already overwhelmed their targets militarily.