At the age of 22 in 1691, he would be given the opportunity to prove himself worthy of his family's legacy. On Easter Day, 100 years after he was defeated by Christopher Belmont, Count Dracula had returned. He was reawakened by a dark order of humans on Easter Day during a dark mass in an abandoned monastery.
Simon was determined to end the threat of a new reign of terror, and entered Dracula's Castle alone to face the Count. Simon slew Dracula's servants and then faced off against Dracula himself as his ancestors had. Unable to kill him in the battle and unbeknown to Simon at the time, Dracula had managed to place a curse on a wound he inflicted on Simon's back.
From the manual for Castlevania II: Simon's Quest:
You're Simon Belmont, bravest of the brave, boldest of the bold, a gothic warrior respected by kings.
You earned your praise, not by crushing Viking invaders or Turkish hordes, but by destroying the evil Count Dracula in a duel to the death at Castlevania.