Here is my theory about Reda, a Character that appears in Assassin's Creed: Origins and Assassin's Creed: Odyssey, also on Reda's ties with the Isu:
As I mentioned, we meet Reda with Bayek in Egypt during the 1st Century BC but under unknown circumstances, we meet Reda again with Eivor in England during the 9th Century AD, it is impossible that a person could live from the rising of the Roman Empire and the end of the Viking age.
Reda was probably an Isu experiment which means that he witnessed the Great Catastrophe, I think that Reda was born probably born during the Isu Age, and he was one of those Humans that were kidnapped to do experiments but he didn't suffer any effects in his physical body but on his age did probably the Isu were searching for a way to live longer.
And he ended by warning Egypt so he saw the Building of the Pyramids, the reign of Tutankhamun, and Ramesses II, but Reda's life changed when he met Bayek, so Reda followed the Hidden Ones, I believed that Reda followed Kawab to Judea, there Reda became known as The Wanderer so Reda also met Jesus.
What do you think? Let me know in the comments below!