Diro, like many Daxamites
, is extremely xenophobic, believing alien influence of any kind would only pollute Daxam
's "purity." As such, he never approved of his son's interest in the stars and the vast universe beyond their home planet (going so far as to break the lenses for Sodam
's telescopes). He was determined to keep Sodam's mind focused on Daxam and its people, and one day have him follow in his footsteps as a senator. One day however, he and his wife eventually discovered that Sodam had been sheltering a stranded alien named Tessog in a cave out in the woods. Diro and his wife had Tessog killed and erased all traces of him having ever existed from the cave (he and Sodam had been teaching each-other using drawings scratched on the cave walls), and had their own son knocked out and put through a brainwashing program that would instill the same irrational hate for anything alien or different that they and most Daxamites felt was the normal and healthy attitude to have on the subject.
However, unknown to Diro, Sodam broke free of his mental conditioning upon seeing his old friend Tessog stuffed and mounted in a Museum (Tessog's face had been altered and his body positioned in such a fashion that he resembled the Daxamite vision of a stereotypical "evil alien monster," hefting a big heavy rock as if to smash the skull of a dummy of a horrified Daxamite "victim"). Sodam pretended to be the son his parents wanted him to be so that he could continue working on restoring Tessog's old spaceship in the hopes of one day escaping Daxam forever (but luckily a green lantern ring found him and gave him an easier means of escape). Diro would not see or hear from his son again until Mongul
invaded and conquered planet Daxam all by himself in record time, then summoned the Sinestro Corps
to the planet with the intention of seizing leadership of the corps in Sinestro's absence and using them to begin his new campaign of terror against the rest of the universe, dispatching them to hunt down and enslave any remaining free Daxamites to serve as his work force.
Diro would send his wife off in Tessog's old ship to hopefully find Sodam and bring him back to help them in their darkest hour (though his surprise at seeing Sodam later suggests he hadn't expected her to succeed and probably just wanted to "spare" her the horror of dying by alien hands, ). He was next seen hiding in a cave by some cliffs along with many of his people, a Sinestro Corps hunting party led by Arkillo
hot on their trail. Diro, believing all was lost, choose to lead his people to commit suicide by throwing themselves over the cliffs rather than live under Sinestro Corps control, or actually put up a fight. Fortunately, Sodam Yat and Arisia
arrived in time to defeat the Sinestro hunting party (Sodam killing them all except for Arkillo, who'd hid in the forest to avoid detection, hoping the two green lanterns would kill Mongul for him) and stop the Daxamites from killing themselves, but sadly some had already jumped under Diro's guidance. Upon seeing his son Diro foolishly believed that they would be able to "mend the fences" later when all was said and done, completely underestimating how much Sodam truly hated him for murdering Tessog and taking away his childhood (going so far as to carry him upside down and hang him over the cliffs long enough to see all the Daxamites he'd led to their untimely deaths out of cowardice).
Diro was also one of the many Daxamites who received super-powers when Sodam Yat used the Ion power to turn Daxam's red sun yellow, seemingly sacrificing himself in the process. When the Daxamites began panicking in response to all the strange new powers they'd acquired, and Arisia went about the process of calming them down and helping them through it, Diro was quite vocal in his dislike for Arisia, believing that thanks to his son's sacrifice the Daxamites had the power to retake their planet and seek revenge against Mongul and the Sinestro Corps without her help. Fortunately, despite Diro's bigotry and anger Arisia managed to convince the Daxamites that the only way to defeat the Sinestro Corps was to master their powers and work together as an underground resistance corps, as opposed to charging headfirst into battle fueled by anger and hate alone.
Under Arisia's leadership the Daxamites drove off Mongul and the Sinestro Corps and retook Daxam (it can be assumed Diro took part in the fight for Daxam though he was never shown doing so). Diro was last seen supervising the disposal of the bodies of the Sinestro Corps soldiers they'd killed, shocking and repulsing Arisia when she caught him ordering a man to toss a still living Sinestro Corpsman into a burning pile of corpses. Diro then made it painfully clear that despite all that Arisia had done for him and his people, despite his son's words concerning how the Green Lanterns fought to protect all the people of the universe & his ultimate sacrifice, he still viewed all alien life as a blight to Daxam and wanted Arisia off his planet immediately (pretty confident that now that they had powers they wouldn't need anyone's assistance ever again). Arisia then bid farewell to the racist senator Diro with a power ring empowered punch to the face powerful enough to make his nose and lips bleed.
After Sodam got purge out of the red sun of Daxam, Diro lead the rest of Daxam to start a hunt for his own son, so that he can throw him back in the sun in order to get back his powers, but Sodam escapes with followers to an other planet, leaving Diro in Daxam with the rest of xenophobic murderes.
Like all Daxamites, Diro Yat gains the powers of flight, invulnerability, heat vision, super-strength, and x-ray vision under the light of a yellow sun.