Just yesterday I witnessed the "self-destruct-mechanism" of the game!

As most players know Riften is far east and thus Stormcloak territory. Ignoring that the game sent an imperial courier to the city...and when he entered all hell broke lose!
The city guard instantly attacked the courier. My dog attacked the city guard. The city guard attacked me because my dog attacked them. Maven Blackbriar attacked the city guard. When the curier went down, Maven didn't stop. As she is essential she always got back up and continued her attack. This would've gone on forever, with her and the guards fighting and every single citizen running like a beheaded chicken trough the town.
Game over!
Luckily I had a few more savegames, thus giving me the chance to see that this "self-desctruct-device" even has a "fuse", and a pretty long one, too. You see, this imperial curier didn't just spawn in the city. When I loaded an older savegame and turned around I could see him running towards the city from at least a mile away (and he probably originated somewhere, too). Half a mile before he reached the city I was able to nicely place an arrow in his back, thus ending the self-destruction-sequence and avoiding to throw away a 210+ hour game!

It amazes and angers me both. Because somewhere in the game logic the AI decided to let a curier start a long run, maybe from the imperial camp in the Rift, or maybe even far in the west, sending him to Riften; and the player can, if choosing the same route, follow him until the catastrophic conclusion. Wow. And on the other hand I would've coursed Bethesda into Oblivion (yeah! *rimshot*) had I not been able to circumvent it!
