(Note: It is not known how much of the original lore from the comics were used in the Guillermo del Toro adaptation)
At some point in ancient times the Ogdru Jahad were trapped in a crystal prison in the coldest regions of outer space.
Despite being physically trapped, they managed to communicate telepathically with other beings, most notably Grigori Rasputin who viewed the creatures as "his god" who chose not to remain silent.
In 1944 Rasputin, with the help of the Nazis, led the Project Ragna Rok to unleash the ancient deities through a portal, in order to lead Nazi-Germany into victory and bring forth a "new Eden".
While the group was able to summon the key to unleash the old ones, known as the Right Hand of Doom into the mortal plain, the project was deemed a failure, as the Allies stormed the ritual-site, killing most of the Nazis and Rasputin was sucked into outer space through the portal. The Right Hand of Doom (later known as Hellboy) was adopted by Trevor Bruttenholm, founder of the B.P.R.D..
Rasputin managed to survive the attack, since the Ogdru Jahad's kin lived now inside him.
The three, with the help of the Sammael, managed to lure Hellboy into an old temple that located near Moscow, Russia, where they would tempt him into releasing the Seven Gods of Chaos. Hellboy refused in the beginning, but agreed when he saw that Rasputin could resurrect his presumed-dead girlfriend Liz Sherman.
As Hellboy used his Right Hand of Doom to release the Ogdru Jahad from the crystal prison and open a portal through a solar eclipse, B.P.R.D-agent John Meyers managed to snap Hellboy out of his duty as the harbinger of the apocalypse, by throwing his late father's crucifix at the half-demon.
Hellboy then managed to close the portal and kill both Rasputin and the Behemoth that served the Seven Gods of Chaos. The Ogdru Jahad were likely put back into their crystal prison.
Unlike the Dragon-like beings from their comic book-source, the Ogdru Jahad from the film, designed by Wayne Barlowe, resemble more the Great Old Ones and Outer Gods of the Cthulhu-Mythos, appearing as massive cephalopods with crustacean-like limbs.
The Ogdru Jahad breaking free from their crystal prison.
An apocalyptic vision in which the Ogdru Jahad rule over the burned Earth with an evil Hellboy.