Alright, let's see how this goes.
It starts with Humans in Alkhazar, trading and talking. Then switches to the Elves in Laurelin, all socializing, and having a good time. And then the Dwarves, in a Tavern celebrating with Pints of Ale. And the Orcs, are mining iron, and making leather.
(These would make Aegis seem peaceful)
And then you switch to the Undead keep, and sweep through the front gate, perhaps up some stairs, and into the Meeting room of the Undead, and the camera rests behind the Undead Overlord. (This could be room for some dialogue) And after the Undead are the done speaking, the Overlord slowly turns his head to the camera, and says "Today, is the End of Aegis. Today, Iblees will Rise."
And then the camera moves to the main part of the Undead Keep, where Undead Initiates are running out of the gates, and heading towards the Capitol cities. And then the sky above the cities gets dark, and lightning starts flashing. And then you see the Undead coming over the hill. And they blow open the Gates of the cities and the Hordes of Zombies and Skeletons start pillaging. The guardsmen come to defend the cities, and then the combat starts, there's fireballs flying everywhere, lightning striking the ground, and just total carnage. The trailer would end with a guard thrusting his sword through an Undeads chest. (Keep in mind that you would see all the different cities fighting the undead, not just one.) And afterwards, an ending screen would say. "Aegis. Join the Fight Today." or "Lord of the Craft, Join the Fight."
Just my idea, was typing this while watching youtube videos.