Whisper

The Whisper was a natural ability of vampires to talk over great distances, in a manner similar to telepathy .It has only appeared in Blood Omen 2. After Kain learnt the use of the Whisper, he was able to keep contact with the Cabal over large distances, enabling him to take extended 'missions' throughout Meridian.

Overview
When Kain awoke after being revived in Chapter 1: The Slums, Umah demonstrated the use of the Whisper to him, calling it a "natural ability" of vampires and implying that all of the vampires (of at least the post-Blood Omen era) possessed the ability.

After Umah taught Kain about the Whisper in Chapter 1 she would again demonstrate it in introducing Kain to the Smuggler's Den in Chapter 2: Creatures of the Night, when she would direct Kain to the The Tavern and Smuggler's Tunnel. Following the trail, Kain met Vorador and the Cabal at the end of Chapter 2, but found that Umah had been captured by the Sarafan whilst investigating the Industrial Quarter. However, before she was captured she had managed to Whsiper to a Cabal Vampire that she had discovered something important within the quarter, leading Kain to be sent to the Upper City and Sarafan Keep to rescue Umah and recover her information.

As Kain made his way through the Upper City in Chapter 4, he was twice called by Vorador, who would direct him to the Bishop's Manor to meet the Bishop and thus find the secret entrance to the Sarafan Keep. Once he entered the keep, Vorador again contacted him using the Whisper to congratulate him on his defeat of Marcus and advise him on the location of Umah. With Kain himself making his way to the Industrial Quarter in Chapter 6, he would shortly thereafter be contacted by Vorador using the Whisper, who gave Kain directions to reach the Main Factory of the complex.

Kain would not use the Whisper for some time after he set off into the Canyons in Chapter 7 and it would not be until Kain returned to Sanctuary with Janos Audron in Chapter 9 that the Cabal were updated as to Kain's progress. Planning their final assault on the Hylden City, Kain and Umah were sent to the Wharves in Chapter 10 to find a way to reach the Hylden City. After murdering Umah for her betrayal, Kain found a ship heading to the Hylden City and was contacted by Vorador using the Whisper who advised him on how to smuggle himself onto the ship. Vorador apparently remained unaware of Umah's death and when whispering to Kain in the Hylden City after the deactivation of the Shield generator, Vorador wished to thank Kain for saving Umah's life (suggesting Umah had contacted Vorador with the Whisper after her injury). Shortly afterward Janos and Vorador teleported to the city, where confirmation of Umah's fate caused "discord" between Kain and Vorador.