name: Matou Zoukenage: looks like and old fart and he actually is more than 200 years old
nationality: Japanese
profession: Magi
family: Shinji (his nephew), Sakura (his niece)
likes: immortality, abusino his niece, evil plots
dislikes: failure.
magic powers: Several being an expert Magi, though his speciality relies in worms
servant: True Assassin
personality: Matou Zouken is an evil old Magi, fellow of those who created the Heaven's Feel system. He's somehow disgusting, not only because of his decadent appearences but also because of his well hided cruelty and the fact that he has always abused of Sakura since she was a child (and he has also encouraged Shinji in doing the same). He has always had the dream to get immortality as his companions for humanity (his intentions were noble at the beginning) , but as the time passed his ideal got distorted and he could merely remember his real motivations behind it. He's a fool after all or simply someone who's carried by a vain hope.
spoilers warning !!!
personal story: Zouken's real lastname is Makiri, one of the magicians families involved in the creation of the Grail war. It seems he changed the surname into Matou just to hide his identity from the Association and protect his plans. He has always been considered a powerful mage and despite his long life span he can't be considered immortal. The truth about it can be found in the worms he controls which carry his spirit from a body to another (they actually eat human flesh and the soul of their host). The main or mother warm was implanted in Sakura's body (the worm is actually the Vessel of the Grail) and Zouken was planning to take its control after the completition of the last war. He doesn't really take part at the 5th War from the beginning, he just enters when he understands time has come for him to strike (and especially after Shinji is defeated). He summons his servant, who happened to be True/Sin Assassin and begun his way to the victory. He soonley defeats Lancer with the help of the Shadow (Sakura) and he let her devours all the other servants she can defeat. The truth is that Zouken has lost any kind of control on her and he can simply watch and hope to be able to win the war. He's eventually defeated by Kotomine Kirei who simply purifies his tainted soul and releases his corrupted spirit.