We learn that Bluebeard is Wullie’s arch-enemy. He hates all humans, although he will work with crooks if he thinks it will help him defeat Wullie. This is how Finn first describes Bluebeard in the bowels of The Rusty Pelican Barge:
The black lump of coal was about three times as tall as Wullie and at least twice as broad. Two fierce red eyes glared out at the terrified Dutchman like burning fires of hatred. As it spoke black gobs of oily spit sprayed out into the air, sizzling when they landed in the fire suspended below. And in the flickering light Finn could make out bright streaks of cobalt blue in the creature’s beard.
As you will see in the later Wullie books Bluebeard becomes a bigger and bigger problem for Wullie. He is a lot more evil, cunning, and determined that you might think after reading Blackhope Scar.