Ultima IX Ascension

Although Lord Brittish is notoriously invulnerable to attack by conventional weapons, there is an easter egg that allows you to slay him. Firstly, when you are in your home (on Earth) at the beginning of the game, you must take the box of rat poison from atop the fridge and then place it upon the electric bread maker. This will produce a loaf of poisoned bread. Take this loaf and carry it with you all the way to Lord Brittish's castle. At the castle, enter the small kitchen (accessible from a hidden door in the banquet hall), where you will find a plate of bread on the table. Replace this bread with your poisoned loaf. Lord Brittish will immediately enter the kitchen and proceed to unwittingly eat the poisonous bread. Shortly after, he keels over and dies.