|“||It's some sort of bullet. It's burrowing through you faster than you can heal.||”|
The self-propelling bullet is a new type high-tech bullet used by the Lycans.
This type of bullet is used by Marius's Lycans as a tracking device against the Vampires. Once deployed it penetrates and drills through the Vampire's body, making them unable to heal and expel the bullet. Instead, the Vampire needs to manually remove it, having to go to a safe place like a Vampire safe house, to perform the removal procedure. Once the Lycans have their safe houses locations, they can invade and destroy it. This was likely one of the ways how Marius and his army were able to find the locations of most of the Vampires safe houses and maybe even some of their Covens.
A group of Lycans were following Selene on Marius orders, in the attempt of capturing her. As she was fighting against them, David who were also tracking Selene, intervened to assist her. Once the fight was over and both let their guard down, Gregor, one of the Lycans that survived the fight, shot a self-propelling bullet at them, which hit David in the abdomen. The pain and impact caused by the bullet drilling through his body made David fell on the ground. Later, when threatened by Marius for failing to capture Selene, Gregor reveals that he shoot her companion and was now able to track them down. Meanwhile, at one of the remaining Vampire's safe houses, Selene helps David to remove the bullet before it makes even more damage to him, there he claims that these new Lycans are more sophisticated, as they are now able to create more efficient weapons against the Vampires. Selene successfully removes the bullet from David's body, and both seemed to be quite worried once they saw the design of the ammunition that the Lycans were using.
Thanks to the tracking device embedded on the projectile, Gregor and a group of Lycans are able to locate the Vampire safe house where Selene and David were hiding. However, by the time they arrive, both had already left with Alexia and a squad of Death Dealers, in route to the Eastern Coven.