Sigmund is a green salamander that was tasked to keep an eye on the Toadstools inside the Castle of the Ancients. He wears a purple leaf hooded cape and carries around a wooden staff.
Since he's completely mute, Sigmund's personality can only be perceived through his actions. From the very beginning, he shows a very friendly demeanour towards the Toad Patrol and does what he can to help them. He teaches them a bit about the Ancients through mimes and charades, and even serves as a confidant to Oyster. Sigmund can appear shy when meeting new people, although it's mostly due to his inability to speak. Once you get to know him, he can loosen up and become pretty silly.
Sigmund's name is carved on his staff, which allowed the Toad Patrol to discover what to call him.