Papa Legba is a spirit often found in Caribbean religions. He is a "gatekeeper". He is called first in religious ceremonies because he is in charge of communication between the spirit world and the human world. His depiction varies depending on location, but his role is usually very similar. He has been compared to St. Peter, because he is in charge of entrance into the other world.
Unbreakable is full of protective symbols – real and fictional – to ward off everything from vengeance spirits and demons to bad luck. You can read about Kami Garcia's inspiration for these on the Legion Series Tumblr (thelegionseries.tumblr.com)