Short answers, pulled from the story.
French Egyptologist Gaston Maspero assigned the title Livre des Portes to an ancient Egyptian funerary text that Egyptians never named themselves. This designation emerged during scholarly efforts to decipher and translate the work from Jean-François Champollion through Erik Hornung and Alexander Piankoff.
The earliest known appearance of this text appears in the tomb of Horemheb, who ruled around 1295 BC. That version remains incomplete compared to later copies found in tombs of the 19th and 20th Dynasties.
Ra guides the deceased soul through twelve distinct hours of night across the underworld landscape. Each hour concludes with a gate guarded by a serpent deity requiring the soul to know its name for safe passage.
Hour five presents the Judgement of Osiris scene where Horus presides over four ethnic groups representing all humanity. Souls face evaluation against evil while enemies await punishment in flames.
Seti I commissioned the first complete inscription decorating his sarcophagus while also covering half the pillared halls with these images. Ramesses II displayed partial scenes on the pillared walls of his own tomb and Ramesses VII included only selected hours within his burial space.