As if the Red Templars weren't already terrifying in the power they wield, the Behemoth bears the remains of a templar's armor. Any templar who ingests Red Lyrium is in danger of becoming one of them. And judging by Meredith's fate, it is doubtful they can survive long even then.
The screenshots of Emprise Du Lion show a tower that has Red Lyrium growing out of it. It's not just in the deepest reaches of the Deep Roads anymore, it's on the surface and it's spreading.
The Breach, the cataclysmic event that tore the Veil asunder occurs during Peace Summit between the various factions in Thedas. As a result, thousands of the people who were at ground-zero were reduced to char-grilled husks, their barbequed remains still frozen either in mid-scream, running or cowering from the devastation. And the Inquisitor is the Sole Survivor of this event.
What has been shown of the new demons indicates that they're pretty creepy, with their weird teeth and mummy-like complexions. The Fear and Terror demons certainly live up to their names.
As the game progresses The Breach becomes larger and larger. Trailers and gameplay videos imply that later on in the game the Breach is large enough that it covers most of the sky above Thedas. The sun is blotted out completely, the skies turn a eerie green, and the floating islands you see in the Fade start to fill the sky.
'The Enemy of Thedas' trailer is a dark, most sinister twist of the previous trailers. Before, it was continuous glorification of the Inquisition and their cause to save the world, but here it's all turn on its head; The Inquisitor and allies are all struggling and being beaten up by the various enemy factions, especially the demons, showing just how completely outpowered and outnumbered we are in this war, and our likely antagonist, the Elder One, whoever of whatever it may be, is the real one who controls the battle, not us.