The Death Egg Mark Four is the fourth model of the Death Egg, a gigantic battle station, built in Mario's world as Bowser's base of operations during the Bowser Saga. Unlike the previous versions of the Death Egg, the rear half of the Death Egg has a design based on Bowser's shell.
The blueprints and schematics of the Death Egg Mark Four were first revealed by Lien-Da after her meeting with Eggman and Bowser. Its schematics are revealed to contain elements from the three previous Death Eggs.
- The Death Egg Mark Four contains combined elements from the first Death Egg (Sonic the Hedgehog 2 to Sonic the Hedgehog 3 & Knuckles), and the Pre-Super Genesis Wave Death Egg and Eggdome from the Archie Comics series.
- The Death Egg's command room possesses the slot machine from Eggman's first base in the Sonic X series.