Greek Gods

Gods are a species of immortal, divine, supreme, supernatural beings, so far the only known gods are the gods of Greek religion. Gods have a unique trait, each one represents a certain aspect of the universe. There are twelve major gods, the Olympians, and many minor ones. Gods are also able to mate/reproduce with non-god beings resulting in demigods.

History
The first six gods and by far the most powerful ones were Poseidon, Hades, Demeter, Hestia, Hera, and Zeus, the sons and daughters of the Titans, Kronos and Rhea. Fearing his children would overthrow him in much the same way he had done his father, Kronos devoured his first two sons and his three daughters after they where born. He would have devoured Zeus as well but Rhea, unable to bear the pain of losing another child and seeing her husband now for what he was, plotted to save her son from the fate of his siblings. Entering into an alliance with Gaia, Rhea was able to smuggle her son away to safety and gave her husband a rock instead to devour. Kronos devoured the rock without question out of arrogance as he had already devoured the other children and he didn't expect his wife to resist him.

After years in hiding, Zeus was finally old enough and strong enough to overthrow his father, and returned to his father's palace to free his siblings who, being immortals, remained alive and undigested within their father all this time. There are many different accounts of how Zeus freed his family but the most famous was when he smuggled a potion in to his father's meal, forcing him to vomit up the children up, and lead the revolt against him.

The war lasted ten years with neither side gaining any true or clear advantage over the other, until finally the gods played a gamble that to some would have been considered suicide. Traveling to the Underworld they released the Cyclops and the Hekatonkheires who had been imprisoned by Kronos; so long has they would aid the gods in battle. They agreed. The Cyclopes forged the Big Three's symbols of power: The Master bolt, the Trident, and the Helm of Darkness, while the sheer strength of the Hekatonkheires proved to be a great advantage against the Titan army.

The final blow came when the Big Three took the fight to their Father. The plan was simple and effective; Hades would use the Helm of Darkness to enter the Titan armory and destroy their weapon which would then allow Poseidon to use the Trident to attack the defenseless soldiers leaving Kronos open to attack by Zeus and the Master bolt. The plan was a success and the final blow was delivered when Zeus using his Father's own scythe; cut Kronos in to a thousand pieces and dropped them in Tartarus where he would (hopefully) never rise again. This marked the end of the Titan age and started the Olympian age.

The Olympians have been challenged many times, but they have always come off on top, with the help of their children, the demigods.

Appearance
When they are covered by The Mist, they are indistinguishable from Humans. Their true divine form is too intense for lesser entities to observe, and if any lesser entity were to look upon a god's true form it would destroy them. A god can show some of this form to a demigod through their eyes, which Percy Jackson has experienced many times. Gods can naturally change between their divine form and their human disguise, but if they become angry enough they will uncontrollably revert to their divine form unless they regain control of their emotions. This happened with Hades in The Last Olympian when he found Maria's dead body. The grief and rage at the sight of her dead body almost caused him to revert to his god state but he was able to regain control of himself so that he didn't vaporize his own children with the force that would have been released with his transformation.

Physiology
Gods do not have DNA or a genetic code. They are composed intirely of magical organic energy, every part of their anatomy is a whole. Their bodies produce a reproductive, organic energy that is the means that they mate/reproduce, the males produce "sperm" while females produce "ovum". When they mate, it produces another god who represents his/her own universal aspect. However they are also able to mate/reproduce with humans, the female "ovum" is able to be fertilized by human sperm and the male "sperm" are able to fertilize a human ovam, resulting in demigods.

Powers
Each god has specific powers based on what they represent, but they all share certain powers and even powers specific to their individual domains can overlap.

However, as a side note, each of the Big Three have a physical domain on earth a.k.a the sky, ocean, and the underworld. This is why the Big Three are the most powerful gods in Olympus.

Powers shared by all tend to include immortality, superhuman strength, speed, agility, durability, senses, ect, and a broad range of magical abilities.

Gods possess a broad range of magical abilities including levitation, teleportation, and conjuring food and walls of fire or doing just about anything they want. The gods seem to all possess telepathic powers as Percy, through the series, experiences this when a god says what's on his mind without him telling them, but it has never truly confirmed. However Artemis once spoke to Percy telepathically in The Titan's Curse supporting this theory. The limits of a god's power in this regard is unknown nor is it known to what extent they can cross into the domain of another. Both Zeus and Poseidon have displayed the power to conjure storms and in ancient myths, Hera demonstrated similar powers, but it is unknown if Ares could conjure a storm himself or if there are limits on what they are allowed to do in this regard.

Gods can appear in multiple places at once if something about their domain is being invoked. Dionysus was able to manifest at a party despite his "true" self being buried under a mountain. It is unknown how many of these "copies" can be made at once, what powers they have or anything else about them.

Gods consume a heavenly food called nectar and ambrosia. It is unknown if they can maintain their powers or live without it.

Rules
Despite their vast powers gods are bound by certain rules. Some of these rules are laid down by Zeus and others are just in the nature of being a god. Only a few of these rules have been explored.


 * No god can directly steal the symbol of power of another. This applies to both the Titans and Olympians and is why Zeus knew a mortal had to have stolen his master bolt as mortals and demigods are exempt from this rule.
 * No god can by force enter the domain of another. The only known god to freely pass between the Underworld is Hermes, the messenger god. It is known this is what prevented Zeus or Poseidon from going to the Underworld themselves to check for the master bolt and that heroes are exempt from this rule. Further details on it are unknown.
 * Gods are limited to how much they can interfere in mortal affairs. This rule appears to be a decree of Zeus and not so much a rule about their nature. It also depends on how much Zeus enforces it or knows about it as gods have been known to interfere when they were not supposed to, with nothing happening to them, like Apollo in The Titan's Curse, or Hera in The Battle of the Labyrinth.