Despite his "unacknowledged" status, Dyron Blackgard was aware of Ethon's existence, as was, obviously, is mother, Luciya Allyrion. However, Dyron refused to publicly confirm Ethon's existence, and Luciya never revealed that she was in fact Ethon's biological mother, which is the reason why Ethon does not hold a bastard surname. If Dyron had officially acknowledged him, he would've been renamed "Ethon Ashes".
Ethon was born as an illegitimate child to Dyron Blackgard and his mistress Luciya Allyrion. Dyron could not raise the child, fearing the scorning, dishonor and humiliation he would receive from his family. Therefore, he refused to acknowledge him and Luciya was forced to take him with her to Godsgrace in Dorne, since the Dornishmen are far more lenient in siring bastards than the rest of the Seven Kingdoms.
Ethon was tutored by his maternal uncle, Daeron Allyrion, in his youth. Daeron quickly became a father figure for the young Ethon. Ethon believed that his father was a farmer and his mother had died giving birth to him, completely oblivious to the fact that Luciya was his mother and that he is in fact a descendant from a powerful and ancient Great House. Because of Daeron's close friendship with House Martell, Ethon was Prince Doran Martell's ward for a number of years and learned a great deal about politics from Doran. Ellaria Sand, the paramour of Doran's younger brother Oberyn, was aware of Ethon's true heritage (her half-sister, Nyssa, was Daeron's wife) and took a liking to Ethon, but never revealed to him his heritage.
Ethon is present at Sunspear when Ellaria proposes killing Myrcella Baratheon as revenge for Oberyn's death at the hands of Ser Gregor Clegane. Ethon is clearly conflicted between revenge for Oberyn and abiding rightful law. Both Ellaria and Doran at separate times try to sway Ethon to their side. Ultimately, Ethon would side with Doran, believing that, even though Oberyn deserved justice, Myrcella was innocent of her family's crimes and didn't deserve to be punished for them. This eventually leads to a rift forming between Ethon and Ellaria when Ethon calls her out on her constant desire to murder an innocent child, going so far as to say that she was no different that the Lannisters.
After Ellaria makes amends with Jaime Lannister and Doran allows him to return to King's Landing with Myrcella, Ethon shows up at the farewell with a bottle of Dornish wine and gives it to Jaime as a show of good faith. During Jaime's boat ride back to King's Landing, when Myrcella is revealed to have been poisoned, Jaime is able to figure out that the wine was laced with the antidote for the poison and tries to give it to her, but it has no effect. Back in Dorne, Ethon is seen staring after the boat, unaware that his plan has failed, looking worried and hopeful.
Ethon witnesses the Coup in Dorne and is initially left shocked, but remains at Sunspear because of how well Ellaria always treated him. However, when House Baerley is named the new Great House of Dorne, the new prince, Drevyn Baerley, is able to learn that Ethon attempted to sabotage the assassination of Myrcella with the laced bottle of wine. An infuriated Ellaria orders Ethon to be executed, but Ethon is able to escape Sunspear and return to Godsgrace, where he would fight alongside Daeron and his loyalists against the rule of House Baerley.
However, when Ellaria and Drevyn declare for Daenerys Targaryen, all hostilities between Daeron's forces and House Baerley cease. Ethon is present during the meeting with Varys and Olenna Tyrell. She tells Ethon that she still hasn't forgiven him for his betrayal of her, but if he was able to help elevate Daenerys to the Iron Throne, there was a chance that she still could.
After discovering his heritage through his mother, Luciya, Ethon decides to travel to Blackgard to confront his biological father, Dyron, and to convince him to openly acknowledge his heritage, cementing his position in the Blackgard family. Once en route to Blackgard, Ethon is approached by a band of mercenaries, led by a man named Vargen. The mercenary leader seems to know Ethon and tells him that he has been sent to kill him. A short fight ensues between Ethon and the mercenaries, but Ethon manages to fend them off. Vargen is preparing to kill him until Ethon throws sand in his face and then rides off, escaping the encounter.
A few days later, Ethon finally arrives at Blackgard and is almost immediately in awe of the Black City. Although still wary of the mercenaries that had been sent to kill him, he decides to stay at the local inn for the night, while reflecting on his journey so far.
The following morning, Ethon continues to head to Ebonheart in hopes of meeting his biological father. While riding in the busy streets of the Bronze District, Ethon stops for an approaching caravan until he discovers Vargen - the same man who tried to kill him - across the road. Vargen instantly recognizes him and sheaths his sword. Ethon gallops towards the mercenary, who is able to kill his horse shortly before being knocked temporarily unconscious. Ethon makes a nasty fall but manages to regain consciousness.
Vargen awakens after a few locals help him up, telling him that a "madman" tried to ride him over. Vargen asks for the man and the locals point him out across the road. Vargen picks up his sword, distressing the citizens, and prepares to attack a bleeding Ethon. Ethon is quickly able to use an innocent bystander as a human shield, blocking Vargen's slash, and makes a run for it.
Vargen chases Ethon down for a few miles until he stops at an arms store in a broken down alleyway. He enters the shop where the shopkeeper looks at him in confusion as Vargen and Ethon begin fist-fighting in the store. Ethon floors Vargen and punches him in the face a few times, while asking who sent him. Ethon picks up Vargen's sword, readying to slit his throat when the shopkeeper points a loaded crossbow at him. The shopkeeper orders Ethon to throw away the sword and to approach him with his hands on the back of his head. Reluctantly, Ethon does so and the shopkeeper hits Ethon's jaw with his crossbow, rendering him unconscious. The shopkeeper looks upon Vargen while rhetorically asking what he should do with him. Eventually, Vargen too, loses consciousness.
Vargen and Ethon awaken in a cellar resembling a torture chamber, gagged and bound to chairs, after the shopkeeper throws cold water on them. He tells them that no one kills anyone in his store except for him or "Laroy". After hearing a few knocks on the cellar door, a second figure, presumably "Laroy" enters the cellar, wearing Blackgard armor. Laroy asks the shopkeeper why the two are beat up, asking him if he "started without [him]". The shopkeeper tells Laroy that Ethon intended to kill Vargen. Laroy inspects the two captives, saying that "they're looking good enough". The shopkeeper asks Laroy which one they "want to do" first. Laroy seems uncertain, to which he rhythmically counts the two. Eventually, Laroy's final count ends up on Vargen, confirming that he is going to rape him. Vargen protests in muffled speeches, but Laroy quickly silences him. Laroy takes Vargen to another room, and the shopkeeper tells Ethon to not try to escape.
After the shopkeeper closes the door behind them, Ethon attempts to remove his restraints, but is visibly struggling to do so. Eventually, he manages to break free and attempts to escape the shop. However, he refuses to leave, and instead decides to exact revenge on the two rapists. He retrieves a sword from the shopkeeper's collection and heads back down to the cellar. He enters the room where Laroy is seen raping Vargen, and Ethon kills the shopkeeper, alerting Laroy and allowing Vargen to crawl away. He holds the sword at Laroy's neck and tries to drive him to pick up the knife next to him. Shortly after, Ethon hears Vargen saying "step aside, bastard". After which Vargen shoots the shopkeeper's crossbow at Laroy's genitals, forcing him to ground. Vargen briefly stands in silence when Ethon asks him "what now", to which Vargen responds that he will bring Laroy to "his men", apparently intending to torture him to death. Ethon corrects himself by asking what will happen now between him and Vargen. Vargen tells him that there has never been a "me and you", and allows Ethon to leave. Ethon asks Vargen why he wanted to kill him in the first place, to which Vargen cryptically replies that he should go to Ebonheart to see for himself. He then tells Ethon to get out, and implores him not to mention this to anyone, saying that if he does, he will personally track him down and "finish the job". Afterwards, the two part ways. Ethon steals Laroy's horse and rides for Ebonheart once more.
Ethon finally arrives at Ebonheart after numerous delays. After arrival, Steffon Blackgard, Ethon's half-brother, initiates the Black Day, resulting in the deaths of hundreds of innocents. Two followers of Steffon, recognizing Ethon, take him captive and drag him into the Pit.
A day after the massacre, Steffon Blackgard, now named "King Althurin the First", visits Ethon in his cell. Ethon, instead believing Althurin to be his torturer, says that if he wants information, he has come to the wrong person. Althurin, instead, says that he merely wants to kill him, and reveals to Ethon that he is his half-brother. Ethon then comes to the realization that it was Althurin who sent Vargen and his mercenaries to kill him. Confused, Ethon asks his brother why he so desperately wants him dead, as he poses no real threat to him, being a nameless bastard who initially knew nothing of his heritage, mockingly asking him if he poses a threat to Althurin - a king's - line in succession. Althurin responds by saying that that leaves Ethon with something to think about while he is imprisoned. Ethon asks Althurin why he does not kill him right now, to which his half-brother responds with that he wanted first to see if Ethon was truly as "godly" as many claimed. Before leaving, Ethon asks Althurin for their father, to which Althurin replied that he has died, visibly upsetting Ethon. Althurin then decides to leave Ethon to rot in the Pit, rather than executing him, showing a bitter hatred towards his bastard half-brother and a desire to see him suffer, for whatever reason.
After being in the Pit for a few days, the grate above Ethon's cell is unlocked and a rope is descending into his cell. Ethon notices three figures handling the rope, one of them a woman somewhere in her 30s. Ethon asks the unknown rescuers why they are attempting to free him, to which they prompt him to hurry, as the guards are sure to take notice. Ethon reluctantly grabs onto the rope and is ascended by the three out of his cell. The three rescuers then leave Blackgard and mount their horses, taking Ethon with them.
The four stop at a camp in the middle of the desert. Ethon begins questioning his female companion about who they are and why they rescued him. The woman reveals herself as Elyse Blackgard, affectionately greeting her bastard nephew. Confused, Ethon asks his aunt why so many have taken an interest in him, to which one of his rescuers replies that Ethon is the centerpiece of a holy war that is about to escalate. The figure introduces himself as Vigilance, a former slave from the Summer Islands who previously belonged to Trevyr Blackgard's household guard. Elyse then tells Ethon that they are taking him to Sunhold in Dorne to meet with Sofina Blackgard, the one heading the resistance movement against King Althurin, where Ethon will learn more about his "destiny".
Smooth, handsome, charming, witty and fully aware of it, Ethon carries himself with an air of supreme confidence (at times, pure arrogance) which is due in part to his exceptional combat skills and tutoring by Daeron Allyrion, who taught him the passions and lifestyles of a true Dornishman. Because of this, Ethon is always sure of success in whatever he does, regardless of whatever obstacles are in his way, and fears no consequences. On the rare occasions where he fails to get what he is after, Ethon usually displays remarkable temper control, often viewing such happenings with amusement and curiosity rather than frustration, likely a byproduct because of Daeron's influence, which also taught him the principles of honor and chivalry; it takes a great personal attack to actually enrage him.
After becoming more accustomed with his role as the Velothine, Ethon receives cryptic memories - presumably from his previous life as Asterion - and due to this his personality changes significantly. He becomes more grim and solemn and quickly loses his witty charisma.