Cerberus works as a guard in the underworld for Hades. This 3 headed dog made sure that there was no mortals that got past the gates, and no dead people that would leave the gates. It is unknown how and when Cerberus was born.
What does Kerberos mean
Cerberus looks mostly like a dog with three heads, but he is huge. Cerberus' tail also looks like something that would be on the back of a snake.
Why is Cerberus so important?
Hades agreed to let cebrus go to the surface under one condition...that Heracles can not use any weapons. Heracles eventually managed to overpower Cerberus and brought him to Eurystheus, this made it so that he successfully compled his twelve labors.
What can this creature teach us?
ME AND YOU SHOULD DO AS MUCH AS WE CAN BEFORE WE DIE!
Kerberos was Cerberus' second name. This second name means "Death-Daemon of the Dark". I think that that name is perfect for such a scary monster.
If we didn't have Cerberus, there would be dead people roaming the mortal world.
PLZ DON'T HURT ME! I HAVE A FAMILY!!!
You could say that this creature taught us to do more than just one thing with our life. All Cerberus ever did before getting overpowered was sit there making sure that no one left, and that unwanted living people didn't get in. That sounds like a horrible life of no sleeping or games. That's a life horribly spent!