Siring

A vampire awaking in transition.

“	"Will these bites turn me into a vampire?" "It's more complicated then that. You have to feed on my blood, then die, then feed on a human. It's a whole ordeal."	”
	— Caroline Forbes and Damon Salvatore in Family Ties

Siring is the magical process humans, werewolves and witches undergo when they are turned into vampires.

Vampire

The vampire transition begins when a human consumes vampire blood, and then dies within 24 hours of its ingestion before the blood can leave his/her system. Afterward, they will awaken several hours later as an undead human in transition to become a vampire. In order to complete the transition, the person must consume a significant amount of human blood, or else they will die within 24 hours.

A human fed vampire blood.

During the transition between awakening after their death and consuming human blood to officially become a vampire, he/she will experience heightened senses, sensitivity towards sunlight, and a general uneasy sick feeling that pushes the person in question to feed and complete the process. A vampire in transition will typically grow in their fangs upon feeding for the first time or just before, and they will develop the rest of their superhuman abilities afterward. If he/she was compelled by a vampire when they were still human, they will regain their lost or altered memories during their transition. Their emotions will be heightened both during and after the transition as well. Humans can eat normal food while in transition, but because of the sensation of being sick, it will likely not taste great, nor will it provide any nutritional value. However, upon completing the transition, food seems to become enjoyable to eat again, though not a substitute for blood in their diet.

Witch blood can be used to complete the transition in addition to regular human blood, and a witch can be turned into a vampire as witches are human. However, most witches will lose their connection to Nature and their ability to practice magic upon completing their transition. Siphoner witches are the only known exception to this rule-- as Siphoner witches do not possess their own magic and can only channel or "siphon" the magic in enchanted objects or supernatural creatures, they retain their abilities after their transitions and can draw on their own vampirism to fuel their magic.

Hybrids

A werewolf feed hybrid blood.

For a werewolf to be sired into a hybrid, they must consume hybrid blood and then they must die, similar to the vampire transition. Werewolves that are sired by Klaus must consume the blood of a human Petrova doppelgänger in order to complete the transition. If they consume the blood of a human other than the doppelgänger, they will begin to bleed from the eyes and nose and then they will start to experience a rabid behavior and in the end they will bleed out and die if they are not mercy-killed beforehand.

The Original hybrid Niklaus Mikaelson is able to have children due to a magical loophole resulting from the fact that he was a werewolf who was turned into a hybrid by magic rather than via another vampire. His children will be born hybrids like his daughter Hope, who is the first truly alive hybrid and the first hybrid to be a practicing witch (as Klaus also has witch heritage from his mother Esther) who also possesses the werewolf gene (inherited from Klaus' father Ansel and Klaus himself) and vampire blood (inherited from Klaus). These born hybrids can also use their blood to turn werewolves into hybrids as well-- the werewolf must drink the blood of the born hybrid prior to their death and afterward in order to complete the transition.

Once the hybrid has completed his/her transition, they will be sire bound to the hybrid who turned them and they will no longer be forced to turn into a wolf during the full moon.