Def Leppard - Volume Four brings together the band's complete recorded output from 2015-2023. The 6-CD set features Def Leppard, Diamond Star Halos and Drastic Symphonies, including 3 discs of Joe Elliott-curated demos, live recordings, alternate mixes and collaborations. Featuring previously unreleased tracks and many appearing on CD for the first time, highlights include The Lost Sessions, rare demos and new 2026 mixes of "Personal Jesus" and "Heroes." Housed in a rigid slipcase with a hardback book featuring Ross Halfin photography, new band interviews and liner notes by Paul Elliott.