Isaac is a Venus Adept, a playable character in Golden Sun, Golden Sun: The Lost Age and a main character in the overall Golden Sun series.
He is the silent protagonist and party leader of the original Golden Sun, and gains a speaking role in his appearance late in Golden Sun: The Lost Age as a co-leader of the game's extended final party. For being the most effective "main representative" of the Golden Sun series, Isaac serves a cameo role in the 2008 Nintendo fighting game, Super Smash Bros. Brawl. He eventually becomes the father of Matthew, the main playable character of Golden Sun: Dark Dawn and husband to Jenna. Isaac is considered to be the most powerful Earth Adept in the Golden Sun series, due to his age at the beginning of his psyenergy training and his adventures across Weyard. His powers are closely followed by fellow Venus Adept Felix and his son Matthew.