After reaching Merlin's cave, Hank writes his story down in a diary and sends letters to his wife. He and his followers plan to blow up all of his factories remotely with dynamite.
He sends out spies and learns that many knights returning from the Crusades are flocking to the Church's banner. The whole country, it seems, has turned against them.
A huge army appears outside the cave. Hank issues a proclamation, congratulating their strength and warning them that he and his men will kill them all if they approach. Once more, we are reminded that knights are just plain stupid: they attack anyway.
He and Clarence anticipate an initial probe from the knights, and power up electric wire to stop them.
They watch as a pair of knights are killed by the wire, followed by many more. (Seriously, guys: chimps can figure this stuff out. If the man in front of you gets killed by the wire, don't touch it.)
The army continues its attack. Hank and his men turn on pumps to create a mighty river on the battlefield, then open up with Gatling guns on the advancing knights. They kill 25,000 without suffering a single casualty.