Blade II

Two years after the events of Blade, a pandemic known as the "Reaper virus" has spread through the vampire community. Infected vampires are turned into Reapers, mutants immune to all vampire weaknesses with the exception of bright light. Unable to contain the Reapers, Vampire Lord Eli Damaskinos sends two emissaries, Asad and his daughter Nyssa, to seek the aid of vampire hunter Blade and his team, consisting of weaponsmith Abraham Whistler and Blade's new assistant Scud. Blade has since recovered Whistler, who has been tortured and held captive by the group of vampires. Whistler had been turned into a vampire by them and after returning to their headquarters, Blade gives Whistler an anti-virus vampire serum to turn him back to human. After meeting with Damaskinos and his human familiar, lawyer Karel Kounen, they cautiously agree to help. Asad then introduces them to The Bloodpack, a group of vampires trained for the sole purpose of killing Blade. In addition to Asad and Nyssa, The Bloodpack consists of Reinhardt, Chupa, Snowman, Verlaine, her lover Lighthammer, and Priest. To keep them in line and after Reinhardt's racially-charged remark, Blade humiliates Reinhardt and plants an explosive charge on the back of Reinhardt's head.
On Blade's advice, the team starts by investigating a local nightclub frequented by vampires. When they do encounter Reapers, they soon discover that their weapons and powers are completely ineffective. Blade is forced to kill Priest after he becomes infected, Lighthammer is wounded (and infected but he keeps this to himself), Whistler deserts his post, and Scud barely survives a Reaper attack by using UV lights to scare them off. One of the Reapers, Jared Nomak, attacks and nearly kills Blade before a burst of sunlight forces him to retreat. Whistler reappears and explains that he has been tracking the Reapers to a central nest in the sewers. Having learned of their prime weakness, he and Scud create UV projectors for the team.
While searching for the nest, Lighthammer succumbs to the infection, killing Snowman and chases Verlaine up a manhole ladder before both die of light exposure when Verlaine removes the manhole cover. Chupa turns on Whistler and attacks him, only to die when a group of Reapers attracted to his scent tear him apart. Whistler survives an encounter with Nomak only because he reveals the truth of his condition and situation to Whistler so he can inform Blade. Asad is ambushed, dragged underwater, and killed. Using a special UV emitter bomb pack, Blade kills all of the Reapers with the exception of Nomak and rescues Reinhardt and Nyssa, but is betrayed by Damaskinos and his people, who stun Blade unconscious.
After Damaskinos' betrayal, he reveals that he created The Reaper virus in order to create a new race of vampires and that Nomak is in fact his son. Scud turns out to be a familiar loyal to Damaskinos, who also works with Reinhardt. Explaining that he always knew of Scud's true allegiance, Blade kills him with the bomb he placed on Reinhardt earlier. Damaskinos then orders his scientists to dissect Blade so that he can learn how to replicate his abilities. After escaping his captors, Whistler brings Blade to a blood pool, where he regains enough strength to kill Reinhardt and his men.
Seeking revenge, Nomak tracks Damaskinos to his private heliport and kills him. He then bites Nyssa, infecting her with the virus. Blade confronts Nomak, and after a ferocious battle, defeats him. With his now-broken sword, Blade stabs it through the side of Nomak's chest and into his bone-protected heart. Nomak then commit suicide to end his suffering by shoving the sword all the way into his wounded heart. Fulfilling Nyssa's dying wish, Blade takes her outside, where she dies while watching the sun rise. The movie ends with Blade in London, where he kills Rush, a vampire he encountered earlier in the movie.

Question: who  reappears and explains that he has been tracking the Reapers to a central nest in the sewers?
Answer: whistler