What is the ruling on one who abandoned prayer for five years, then repented and died unaware of the obligation to make up the missed prayers?

The mentioned individual is a Muslim; they should be washed, prayed over, and buried in Muslim cemeteries. Their affair is with Allah. If they missed the prayers out of ignorance, it is hoped that they will not be punished. It is not legislated for anyone to make up prayers on their behalf. What is obligatory upon one who has missed many prayers is to make them up to the best of their ability. If they repent sincerely and begin making up the prayers, then die before completion, it is hoped that Allah will forgive them because they did what they could, and "The one who repents from a sin is like one who has no sin."