Ally or not, Willem is under the spell of a terrible entity and must be stopped before there is any further loss of life. You shout for the troops to engage. The unnatural force coursing through his body gives Willem incredible strength, and he manages to fell several of your men before you can take him down.

With Willem's body dead on the ground, the shadows recede once again. You were responsible for the brave young squire, and now he has paid the ultimate price for trusting you. There is nothing else to be said as you continue on toward the Spire, leaving his corpse behind you.