To kill intruders and to protect his treasure. He redeemed himself by finally parting with it (a disk piece) and making sure the gang made it out as his house finally gave way, sinking too deep to survive.
"Big, fat, insecure know-it-all? Who's that? Oh, come on. I wouldn't exactly describe myself as big, or fat or insecure. Am I? (Shaggy and Scooby looking at her disagreeably). (Velma looking sternly back at them) Why aren't you two supportively agreeing with me? Huh? What? Oh, uh sorry. Um, you're awesome."
— Shaggy, Scooby and Velma '