Cortez appears as as a giant skull wearing a Pirate's hat with solid blue eyes. During the battle with Mario, he has four skeleton arms utilizing several types of weapons (Hook, Sabre, Rapier, and a Cutlass).
At the first glance, Cortez behaves eerily, talking in a moaning, spooky voice to warn anyone who approaches his ship. When encounter, he swiftly reveals his true personality as a merciless pirate. He talks with a pirate dialect and wastes no time battling Mario. Though he is revealed to be somewhat honorable after the conflict as he concedes defeat and takes time to listen to Mario rather than needlessly continue the battle since he's immortal. He's also fairly reasonable since he gave the Sapphire Star to Mario without any fuss after he clarifies that that's all he wants since it was just one jewel in his entire collection that he didn't even pay attention to. After the chapter, Cortez seems to lighten up, becoming helpful and friendly towards others, as well as freely offers Mario and his allies quick rides from Rogueport to Keelhaul Key and back on his ship without any catches.