Lezard is an accomplished Alchemist as well as a practitioner in the dark art of Necromancy. At some point between his school days at the Flenceburg Sorcery Academy and the start of the game Lezard finds the legendary Philosopher's Stone. Although, a more atp description of the Stone would be 'the ten-billion-page codec...' that contains all of the world's knowledge. The Stone, however, does not bestow all of the world's knowledge suddenly after obtaining it... it must be read. Once Lezard gained access to the this knowledge he became the most dangerous human on Midgard.
He used the Stone to learn ancient magicks and inscribed forbidden runes onto his castle; the fourth (undoes any chain or binding), the fourteenth (imparts knowledge of the gods and the elves to another) and an unknown twenty second rune. Lezard also learned about the gods that govern the mortal world and comes to understand that Odin is the only god that is half-elf, meaning he can grow just as mortals do. Deep within the bowels of his tower, Lezard carries out experiments on the elves he has stolen from the Forest of Spirits. He creates homunculus vessels that are half-elf in hopes of transferring Lenneth's soul into one, turning her into a human.
Lezard develops a deep infatuation and obsession with Lenneth Valkyrie. The games doesn't go into how Lezard falls in love with Lenneth, but from the moment he first sees her, he is quite taken. This obsession goes so deep that in order to draw Lenneth to him Lezard kidnaps the husband of his former professor, Lorenta. When she arrives she is killed by her husband who has transformed into a ghoul after being given Ghoul Powder by Lezard. This depraved act causes Lenneth to appear and confront Lezard in the depths of his tower. When Lenneth attempts to defeat Lezard in battle, he makes a hasty retreat and teleports away. Lenneth goes on to destroy all of Lezard's constructs before leaving Lezard's tower.
During Ending A Lezard lends his powers to Arngrim and Mystina in order to restore Lenneth's body. To do this they use his final homunculus (found in Mystina's lab). After the credits, Lezard states that he had to give up Philosopher's Stone or he would have been consumed by the Dragon Orb's final flame. However, Valkyrie's transformation has thought him everything... he now has the confidence to realise his greatest dreams and ambitions. Lezard also adds that his is the only soul not controlled by Lenneth, but that she has captured his soul in another way. He finishes swearing that ultimate power will be his, by it own hand it will be his.
Assuming you are playing on hard mode and have at least one Flame Jewel, Lezard becomes a playable character in the Seraphic Gate. The door to reach him is located in fifth room on the second level of the dungeon. Lezard is without question the most powerful mage in the game, but you must first defeat him in battle before he will join your party.