Who is Nicholas Flamel from The Magician and what is their importance?

Nicholas Flamel is an alchemist who lived in the fourteenth century. Flamel came across the Book of Abraham during his lifetime and realized it was something that needed to be protected from those who did not have the best interests of humans in mind. For this reason, Flamel began using a potion in the book that gave him immortality. However, this potion changes every month, but must be administered every month to keep the benefits.