Complex sentence: Garrick only made guest appearances for most of the 60s and 70s, but in 1976 he became a regular character in the revived "All-Star Comics", partaking in adventures with the Justice Society set in modern times.
Split into simpler sentences: Garrick only made guest appearances for most of the 60s and 70s. However, starting in 1976, Garrick became a regular character in the revived "All-Star Comics", partaking in adventures with the Justice Society, in stories set in modern times.