Ah, the Old Gods - obviously modeled after Lovecraft's eldritch horrors. The last expansion focused on areas like Uldum and Uldaman, extremely ancient Titan civilizations, but the Old Gods are older then that. They used to rule the primordial Azeroth before the arrival of the Titans (basically demigods) who sealed them deep in prisons, but their influence still manages to leak out.
So far there is -
C'thun in The Temple of Ahn'Qiraj, 40man Vanilla WoW raid.
Yogg-Saron in Ulduar, Wrath of the Lich King Raid.
N'zoth, likely imprisoned deep, deep beneath Azeroth's oceans. Source of the corruption in the Emerald Dream (Ysera's realm) and Deathwing's madness.
Y'shaarj, who was killed by the Titans eons ago. Old Gods don't really die though, nor are they really alive either, for they exist beyond the cycle of life and death. What remains of Y'shaarj was his heart, imprisoned beneath the Vale of Eternal Blossoms in Pandaria. Y'shaarj is responsible for the Sha, manifestations of Anger, Despair, Fear, Doubt, Hatred, Violence and the most powerful of all - Pride.
There are probably others. The Elemental Lords - Ragnaros, Al'akir, Neptulon and Therazane were/are their servants, so Therazane will probably be added if true. They have many, many worshipers springing from all over encompassing many races - the Naga, the Qiraji, the Nerubians, the Mantid, tribes of Orcs and ogres, the Twilight's Hammer encompassing humans, trolls, tauren, dwarves and everyone else, dragons...pretty much everyone.
I didn't watch the video, but the keyword being "Whisper" makes sense. Old Gods, even deprived of most of their powers have the ability via telekinesis to speak inside the minds of mortals.
O I could be lucky enough to own c'thun or yogg...wait I got shit luck, I'll never get them if they are cards)
