The Desolate One
Lord of the Shadows
Harbinger of Pestilence
Seed of Destruction
Hound of Resurrection
Sammael the Desolate One, also known as Lord of the Shadows, Harbinger of Pestilence, Seed of Destruction, and Hound of Resurrection, was one of the main antagonists in the Hellboy film. Sammael is a hellhound in which his essence was preserved and sealed within salt; crystals formed and gathered from the tears of a thousand angels. He was described as a “Son of Nergal”, one of the seven Ogdru-Jahad, which implies that he is an Ogdru Hem. When Sammael was brought forth in the modern world of 2004, the creature was cast with a spell by Grigori Rasputin, where for each “one of [him] that falls, two shall arise“.
Aside from the obvious superior strength and agility he possesses, Sammael also possessed incredible regenerative abilities, earning him the title of “Hound of Resurrection”. This allowed him to dislocate his limbs to reach in directions that most creatures cannot, with any broken bones or sustained injury inflicted on his body can be regenerated back to its original form. However this does not mean that Sammael is immune to death as grievously injuring his body is known to incapacitate him for several minutes. Therefore, it was shown to be extremely difficult to fatally injure the creature, as it took explosions, electricution, incineration, and otherwise extreme bodily damage, such as being crushed, to for him to be killed. This was negated by Sammael’s ability to split his essence into two, allowing him to be reborn and grow in numbers each time one falls.
Each Sammael was capable of laying a cluster eggs, specifically in dark and wet environments, as they were sensitive to heat and light. When one Sammael was killed, two of these eggs break away and rapidly matured until there were twin clones of the monster. This process repeated itself every time one was killed, thereby allowing Sammael to multiply himself and grow in numbers.
In the movie, it was implied that the only known way to permanently destroy Sammael without causing him to be reborn is to destroy all the cluster of eggs along with any available clones of the creature in one fell swoop. Though, considering his essence had been magically bound with the tears of a thousand angels in the first place, either it was an unnecessary religious precaution to prevent a possible resurrection or Sammael could be resurrected from mere bones and ashes, as Rasputin demonstrated.
In the very last scene of the first movie, a roar is heard. Sammael isn’t shown to be the one to have produced the sound but it hints to the protagonists’ failure at getting rid of the Hound of Resurrection which could either give ground to the above theory or simply means they weren’t able to destroy all the eggs.