Complex sentence: Mark Kelson began his music career in the doom band Cryptal Darkness, after 3 full length albums and several personal differences in the band, Mark left the band to begin his most successful band to date The Eternal.
Split into simpler sentences: Mark Kelson began his music career in the doom band Cryptal Darkness. After 3 full length albums and several personal differences in the band, Mark left the band to begin his most successful project to date The Eternal.