Killing Kerghan and using the vendigroth device on him. Then seeing the bit of movie were you see the use of the device (with all the spades going through him). And then to see the ending saying "together with kerghan you have destroyed all of arcanum and kerghen turned onto you, you have to wait until you die as last person in arcanum". Placing the stillwater sword in the Bangellian Furnace because you didn't had enough room to pick up the bangellian sword/axe? This offcourse the first time ... and beeing the kind of player who tries to finish the game without reloading. Yes, I learned a lesson there.