Samos has appeared in every Jak game on the PS2 and is one of the major characters in the games. It should be noted, however, that the following will contain SPOILERS.
Jak and Daxter: The Precursor Legacy
Samos is one of four sages that are most knowledgeable about each of the different types of Eco. Samos, also known as the Green Sage, lives in Sandover Village where he is in charge of harvesting and channeling green Eco. When Daxter is accidentally transformed into an ottsel, Samos sends Jak and Daxter to find Gol and on the way open all of the teleporter gates at each of the sages' homes. When Jak and Daxter arrive at the Blue Sage's hut, they discover that it has been ransacked and the Blue Sage is gone. Samos begins looking for the sage. When Jak and Daxter find that the Red Sage is missing as well, Gol appears and reveals that he has been kidnapping the sages and forcing them to power an ancient Precursor machine he needs to open the last silo of Dark Eco. Samos is later kidnapped as well, but Jak and Daxter free him, as well as the other sages. Using their combined powers, the four sages produce white eco, which Jak and Daxter use to defeat Gol and his Precursor Machine.
In Jak II, when Jak and Daxter are meeting "The Shadow", they find out that the Shadow is a Samos. Jak and Daxter do not know how to explain how this is the Samos. Young Samos is exactly the same as his older self. When Jak and Daxter have to break in KG Headquarters to rescue his friends he finds the older Samos in the jail who is angry at Jak and Daxter for not saving them earlier. When young Samos and old Samos meet at the Underground hideout to discuss plans the fight most of the time they are trying to explain things to Jak. Later old Samos tells Jak that he has to take young Samos to Haven Forrest and protect from the Krimson Guard so he can work on his Eco powers. In the end when Jak defeats Kor (Leader of the Metal Heads), a Young Samos and young Jak travel on a machine Keira built so that they could travel back in time to the time around the game Jak and Daxter: The Precursor Legacy