Baldi is a creature that appears in Baldi's Basics, with a random change of appearing in almost any floor. (Specifically ones made by FerbFletcher who made most of the floors) (NOTE) The ground has to flat on that floor for him to spawn.
Baldi also works like a security guard that kills players that are cheating. Baldi also has the ability to kick - if you type into chat a forbidden word, you will be kicked.