I'm surprised this doesn't translate anywhere in his gameplay. Poor fit? Or was it just not thought of when he was first created?
It'd be kinda cool if he set off an explosion when he died ala Kog'Maw, but I'm guessing that would be rather frustrating for attackers to require compensating for.
All of our characters have built in ironies:
Xerath was powerless. Now he is so powerful he is only barely contained.
Xerath was a slave, he thought that by getting power he would become free of his chains. But now, with power, Xerath's chains are all that keep him from exploding (dying).
TL;DR: According to the lore, Xerath is an ascended being, and the "magical nuclear reactor" thing he has is a sarcophagus (see: fancy stone coffin) that was sealed with blessed chains and powerful sigils of binding. I would highly recommend checking out Shurima's lore as it is an incredible read.
http://leagueoflegends.wikia.com/wiki/Xerath/Background
https://www.youtube.com/watch?v=JKnM6Hh5gOg
https://www.youtube.com/watch?v=CYyuH1Bp2ZI
Xerath was the son of captured scholars - doomed to be a Shuriman slave for all of his life. His father was crippled and left to die during an excavation, and his mother begged an architect to have him as an apprentice. The architect noticed Xerath was an exceptional learner, and sent him off on various knowledge-gathering expeditions on a daily basis. One day, Xerath met Azir (the last in line, at the time, to be emperor) and assisted him with deciphering an ancient text. The two became friends (which was unheard of for royalty to befriend slaves) and Azir gave Xerath his name, which translates to "one who shares."
Azir's brothers all died in an assassination attempt, but Xerath saved Azir. Azir was then next in line for the throne. Xerath also insisted that Azir learned to fight to survive. As Azir and Xerath grew older, Azir relied more upon him for guidance and assistance. Xerath continued learning everything, however secretly desired to become a free man - going as far as corrupting the unborn infants inside Azir's wife's womb, calling a lightning bolt into the queen's chamber and killing the firstborn prince, and murdering those who spoke of a curse. Xerath justified this in his mind as keeping his friend safe.
Azir was crowned Emperor of Shurima, and Xerath expected Azir to end slavery at that time. Azir did not. Xerath lost all faith in the morality of Shurima.
Renekton and Nasus have proven that mere mortals could be ascended and did not need to be specially chosen by the Sun Priests, so Xerath plotted to ascend himself one day. He distracted the brothers by weakening the seal on a magical sarcophagus containing "a beast of living fire" (Brand?) to ensure nobody was able to stop him. Azir had finally planned to ascend, and this was Xerath's perfect opportunity to gain his freedom. But prior to his ascension, Azir turned to Xerath and announced he was a free man, and renounced all slavery in Shurima before naming Xerath as his eternal brother. Xerath was stunned, but this would not stop his plan to ascend.
He then blasted Azir, burning his friend to ash, before then taking in the power of the sun himself and ascending - however the power was not his to take and transformed his body into an Ascended being. The power of the sun then destroyed Shurima's legacy, bringing ruination to nearly everything and killing most of the inhabitants.
Renekton and Nasus saw the storm, and rushed to find what happened, attempting to seal Xerath in a sarcophagus sealed with blessed chains and powerful sigils of binding. He shattered the sarcophagus, but the chains and remnants remained bound to him. The brothers were equally matched by Xerath's incredible power, but dragged him to the Tomb of the Emperors, where locks only answered to the blood of Emperors. Renekton held Xerath in the tomb and commanded Nasus to seal him in behind him. Nasus reluctantly did so. Renekton and Xerath then began an eternal battle in darkness - this is where Renekton's corruption and hatred for his brother comes from, as Xerath's heavy influences drove Renekton to insanity.
Renekton and Xerath were freed when Cassiopeia and Sivir came raiding into the vault, and Cassiopeia betrayed Sivir by stabbing her in the back (literally) to steal her weapon and use it as a magical key to unlock a vault. This vault is what sealed Xerath away with Nasus. Cassiopeia was bitten by the snake guardian/statue that came to life and transformed her body into what it is today. As Sivir lied bleeding, her blood (royal, descendant of Azir) soaked into the sands, and ignites a deep magic resurrecting Azir.
This is just a super short version of the entire lore, again I'd highly recommend reading it and watching the videos, as they are very intriguing!
It'd be kinda cool if he set off an explosion when he died ala Kog'Maw, but I'm guessing that would be rather frustrating for attackers to require compensating for.
Well... His death animation DOES that... Sure, it doesnt deal damage, but its something.
With the current state of his character, I guess you could say he does satisfy a couple properties of a nuclear reactor, but more like one that has had a meltdown:
Some recent games that he was in have shown him to cause global damage, similar to radiation, since Summoner's rift is not large enough for that amount of radiation to decay. This would imply that him, being a "magical nuclear reactor", is going through a "meltdown"
