Divine Form

The Divine Form is the true immortal form of the gods in which all of their essence is in one place. Looking upon a god in this state will incinerate and destroy any mortal onlooker. Titans also have a divine form, which differs from that of the Olympians in that they are able to destroy mortal beings simply by being in their very presence. It is unknown if this is because the divine form of a Titan is more powerful than that of a god, it may simply be more volatile and chaotic, or it could also be the gods have either better control over this ability, or more reason to control it. It grows brighter when a god or Titan is angry.

Description
Gods in this fully manifested state are roughly humanoid beings radiant with the true, unbridled power of their divine essence. Their bodies are enveloped in an intense light, which seems to differ in color based on the god, along with waves of power and energy which is capable of decimating everything in visual range. Mortals cannot witness a god in this form, lest they burn up from the sight. This does not seem to apply when the mortal is present in spirit and not in body, as Jason survived a demonstration of Hera's divine form when she appeared to him in a dream.

The Last Olympian
Percy describes Oceanus and Poseidon's clash as 'streaks of green and blue... as if the sea itself was torn apart by the two armies.'

The Lost Hero
Hera transforms into her divine form in the battle at the Wolf House, defeating all of the mosters and presumably killing her champion, Jason Grace. A ring of force is left behind after she returns to her normal form. Jason had made the mistake of looking at Hera when she appeared in her divine form and describes it as looking like a super nova. He came back to life using the Doors of Death along with Pipers help.

Trivia

 * While the gods took on their divine forms to attack Typhon, the campers at Camp Half-Blood were able to witness the battle safely, using an Iris Message.
 * Jason Grace is the only known being to survive seeing a god's divine form.
 * Greek mythology did provide some perspective of there being a divine form. One such myth that presented a god in divine form would be that of Zeus and Semele. Semele, who was pregnant with Dionysus, was tricked by Hera into begging Zeus to see his divine form. Zeus was compelled to agree by a promise he'd made on the River Styx and the result was fatal. He only just saved the infant Dionysus in time. Dionysus could then be considered another being known to have survived a god's divine form.