The God of Lies

The fourth God to arrive on Earth was an array fragment built of necrotic energy. This landed in the Atlantic ocean, and released waves of noxious energy through the oceans. Only the most fortuitous creatures were able to survive this event, which led to the deaths of vast amounts of ocean-life, as well as creating uncountable issues across any species that used the oceans as a food source. This is what is referred to as the fourth extinction event, the Triassic-jurassic Extinction, 210 million years ago. 
This allowed for the growth of the array fragment into a Geocarpic Omniscient Particle, taking on the governance in opposition to the God of Growth as the God of Decay. It is through this that it is theorized by the Guild of Architecture that, when in metamorphosis from an array fragment into a Geocarpic Omniscient Particle, if there is currently an already existing Geocarpic Omniscient Particle that is governing freely over any aspect without opposition, then the Geocarpic Omniscient Particle will take on governance of it's most natural opposing force. 
This would explain why the Particle then became the God of Decay, taking on the governance of decay. The biggest negative effect that came from this was the proliferation of infection. It remained this way up until the humanization, where it was then evolved alongside The God of Truth. Being it's natural opposition as Decay, and taken that the God of Growth was now taking on the governance of Truth, it was natural that the decay of truth would mean lead to formation of the God of Lies.
As the God of Lies, it's influence seems to be the most direct. The want to withhold information, change information, or create false narratives grew naturally within humanity in the early days of the Highmortals on Earth, so enhancing this with the inherent greed and urge that led to the proliferation of the lie was not a hard imprint for the newly formed God to make. 
Followers of The God of Lies are the most few, as any larger organization built towards the concept has a tendency to implode eventually for obvious reasons. 
Agents of the God of Lies tend to be agents of chaos. Good, bad, and in-between, these devotees tend to work independently, sowing webs of lies to serve some inner purpose.

"The God of Lies is not evil, as much as the name implies. It is instead chaos. Pure chaos. True followers see themselves the harvesters of chaos, as well as the select few who see the secret reasoning behind the web."

Guild of Architechture