Originally Posted by
haiyken
Before the events of Warcraft III, there would be a lot of change to the timeline and especially regarding Medivh. We know he's under the influence of Sargeras even before being born. What would be Sargeras' plan if Medivh failed to bring the Orcs to Azeroth through the Dark Portal? What's the next thing he could have done?
My guess is on trying to corrupt other races, especially humans since they're pretty prone to it. Maybe not by fel magic, but it's just easy to create conflict. At this point in time, most human kingdoms are devided and don't trust each other. Kingdoms like Alterac and Stromgarde just hated each other. Even Genn Greymane didn't believe in the alliance of kingdoms during the first and second war, only sending gilnean troops to keep the trade relationships going with other kingdoms. Without a large and foreign enemy like the orcs, there is little doubt an alliance would never be created. Sargeras would probably use Medivh to corrupt cities like Dalaran from within, maybe work with Dreadlords to instigate chaos in their ranks.
I don't think there are races prone to fel corruption like the Orcs on Azeroth. Maybe the Trolls, as they're known for their Berserking ability. I can imagine Sargeras/Medivh being able to manipulate Trolls beliefs in a Loa that would make them take on demon blood (or something similar) to enslave them with fel magic. But while it could be a possibility, I don't see that happening on the same scale as the Orcs because their situation would be really different. Troll aren't driven my combat and war like the Orcs are, so I don't think the same thing could happen.
Without the orcs invading Azeroth, I think the timeline would change drastically. It's very probably the Eastern Kingdoms would be heavily controlled by human kingdoms, expanding a lot more in all regions. It's probable the human kingdoms would have enough ressources to help the High Elves crush the forest Trolls once and for all, securing all of the northern part of the continent. No wars means also a lot of things: no Defias brotherhood as Stormwind never gets destroyed, but also no Silver Hand (and a lot less paladins) as they were a direct response to the orcish invasion and the rise of Death Knights. Characters like Turalyon don't rise to be heroes and inspire the forming of the Alliance. Khadgar probably doesn't kill Medivh, doesn't age, and doesn't become the new Gardian in the future.
It's possible Sargeras and Kil'jaeden could still put into motion their plan to create the Lich King, and maybe still use Ner'zul trapped into the armor. Frostmourne would still exist but is it possible Arthas' destiny would not be the same? Arthas wouldn't have grew up in a worn torn kingdom and, probably, wouldn't have the need to be trained as a paladin (if that order even existed). Arthas was arrogant and self-righteous even before getting his hands on Frostmourne, wich, without a war, would probably push him more into politics than anything else, especially if other human kingdoms were still around and fighting with Lordaeron. In the event of the plague coming to the Eastern Kingdoms, it's probable the story would unfold the same way, because Arthas would still do anything to protect his kingdoms. But would Stratholme end up different? This is the turning point of Arthas' story. Any drastic change in his life until that point could make him make a different decision.
A lot of other events could change a lot without the orcs (but it's not really about the orcs but much more about the wars their invasion created), and the changes get bigger and bigger when this alternative timeline progresses.