My players had a ton of fun with the opening. Like some others, I started before the official opening. I had everyone briefly discuss why they were in Kenabres, gave a quick rundown of the history of the region and explained the significance of Armasse.
Afterwards, I plopped them into the festivities of Armasse, took the role of a couple carnival barkers. One of the games two players stepped up to play was my way of introducing the mass combat rules.
Because Armasse grew out of a need to teach religious and military history, I set it up as a board game scenario of Iomedae's 4th Act. One player took control of Iomedae's knights, the other took control of the bigger Wraith army. That was fun, and laid the groundwork for some future concepts.
The other 3 took archery, swordplay, and history challenges against citizens, one of whom was Anevia, another of whom was a young man who took a huge shine to the paladin. They won a huge melon as a prize, but upon cutting it open, a trio of giant maggots were infesting it. They dispatched them without trouble, but the crowd thought it an ominous portent.
At noon, they moved to the plaza to see Mayor Hulrun's speech, but he started coughing heavily as he tried to deliver it, eventually collapsing to his knees. He coughed until a cockroach wormed its way out of his mouth, and he and the crowd watched it scuttle away in revulsion. At that moment the Kite exploded and Khorramzadeh appeared.
All hell broke loose, and a passing Eagle Knight ordered civilians to get to the lower levels of the city. The PCs all fell back as demons started pouring into the city, the ground quaking violently, and vermin bursting out of cracks in the earth.
In the plaza of St. Clydwell, the PCs stopped to pull rubble off of some civilians, as well as slice through a couple giant cockroaches and flies that were terrorizing people. After a few rounds of that, Terendelev crashed through the upper reaches of the cathedral with Khorramzadeh atop her. An Ulkreth loomed up over a row of buildings and slammed its fist down, sending the PCs tumbling. Terendelev cast feather fall, and from that point on, I basically ran it as written.
The players seemed pretty pumped with the opening, and I'm glad I got the opportunity to introduce some later concepts and NPCs as well as making the beginning very epic. It was a ton of fun.