Noxus

right|300px 
Even though the Netherworld is filled with vile, atrocious creatures, there is one Netherlord that stands out as the most unclean, repulsive of them all: Noxus, the Netherlord of disease. This unclean, filthy deity has taken the lives of thousands and his name is cursed every time by the bereaved. Although trapped in the Netherword, Noxus' diseases and infections yet contaminate The Mortal Realm, although his full strength is yet held back by the barrier between The Mortal Realm and The Netherworld. Should this barrier ever be broken, Noxus will let his diseases and plagues wash across the world, devouring everything in its path like disgusting wildfire.
Although the barrier has never been truly shattered, it happens at times that small holes are made in it, to allow creatures to slip through. One of these creatures could very well be Noxus' prime creation: the plaguefiend. A hulking abomination, at least 5 meters tall and composed purely of rotting, decaying material, this creature is truly dreadful. Merely being in its vicinity can be deadly, as it spreads plague wherever it treads. Those who summon this atrocity often wear some kind of protection, so that their bodies don't end up as part of the creature they summoned.
It is common that the Netherlords once lived in the Aetherworld, and Noxus is no exception. In primordial times, Noxus (who at that time was known as 'Issec') was the spirit of insects. His power was small, puny compared to his brethren spirits. Seeing how the spirits around him ruled over things like water, war, love and the likes, Noxus (Issec) grew envious. He wanted the same power, he wanted to be recognized as a great spirit as well. And that's when he got a vile idea. To prove his power, he unleashed plagues of insects upon fertile areas that were quickly eaten down by his unstoppable swarms. In the Aetherworld, he grinned as he saw what havoc his swarms unleashed and hoped to be recognized for what he truly was capable of. And he was, but just not in the way he'd want. The spirits frowned upon him and cast him out of the Aetherworld, into the Netherworld where Locux welcomed him. And here he grew bitter and vengeful, and changed his name and purpose. He began to cultivate his diseases and eventually created the plaguefiend, his masterpiece of rot and disease.