In terms of lore, this appears to be because it's one of the strongest and smartest entities in the game. When does Roblox Doors' Figure appear? Figure appears on floor 50, and later at floor 100.

Level 50 is one of the hardest levels you can beat in Roblox Doors. In this level, you are in a library with a giant monster trying to hunt you that is known as Figure. And while it doesn’t have any ...