Old Knight William is a boss in BLACKSOULS 2 that appears in the Spore Forest after passing through the fog where you can encounter Pumpkin-O’. Before fighting him, under certain conditions, you’ll be able to summon the Knight in Armor and/or Pumpkin-O’ to help you defeat him, and they’re of significant help, especially if you’re weak.
He’s most likely based on Lewis Carroll’s poem You Are Old, Father William, which appears in his book, Alice in Wonderland.
Old Knight William has a lot of health and he’s slow with his attacks, but they’re deadly. Especially watch out for when he gets into the second phase of the fight.
Killing Old Knight William will give you the Soul of the Old Knight and a Great Sword. You will also get a fairytale a Knight in Armor if you had him fight with you.
