Complex sentence: As The Undertaker, Calaway's gimmick was a horror-themed, macabre entity who employed scare tactics and held links to the supernatural; the character was reinvented as a biker during a period in the early 2000s before returning to his previous gimmick in 2004.
Split into simpler sentences: As The Undertaker, Calaway's gimmick was a horror-themed, macabre entity who employed scare tactics and held links to the supernatural. The character was reinvented as a biker during a period in the early 2000s before returning to his previous gimmick in 2004.