I think both Yogg and the Lich King was aware of Algalon. Notice in Yogg's visions he is certain almost cocky that the end is coming for LK and for everyone. His visions also prove something vital - that Azeroth is corrupted. Wheter Yogg influenced these events is questionable. But he certainly planned on using the visions as evidence of corruption. It showed mortals could be corrupted.
Now why hasn't LK destroyed Yogg himself? Perhaps he is not capable? However Yogg would have almost certainly attempted to whisper to LK and LK having powerful psychic powers of his own must have resisted these whispers. He might have even turned it around and gained wisdom from Yogg. If he did then LK would also know about Algalon's arrival and Re-origination.
The Scourge hate Yogg as revealed in a questline. This must be because LK knows what Yogg is going to do when Algalon arrives. He will present the evidence and Re-origination will commence.
Had LK gone into Ulduar and defeated Yogg (to prevent his squealing to Algalon) and then confronted Algalon, then this would have shown Algalon all the proof he needed that Azeroth is corrupted. So LK left Yogg alone, knowing full well adventurers would seek the secrets of Ulduar, defeat Yogg and then learn about Algalon. Algalon only stopped the sequence because he saw good in the hereos, this is something LK could certainly not achieve.
- Most of what you said makes sense, but I'm not sure Algalon would just use the small sample size of heroes he happened to encounter in Ulduar to judge all of Azeroth. Also, according to the Archivum Console: "Algalon diagnostics assess danger of systemic Old God corruption in planetary vital functions." So, if the Lich King knew of Algalon and Yogg-Saron, he would have motivation to kill Yogg to prevent "re-origination", because that would mean the end of the LK also. Killing Yogg would seem to be the primary proof that the Old Gods haven't irretrievably corrupted Azeroth, since killing any Old God should show corruption could be prevented.
- It would really have been more interesting if Algalon or the Archivum Console mentioned C'Thun's death in the Temple of Ahn'Qiraj. However, it may be that what we kill are not the Old Gods themselves, but projections in Azeroth similar to Ragnaros in Molten Core.
- The real question is whether Algalon was aware of the Lich King. -- (talk · contr) 24 Jun 2011 11:12 AM Pacific