The Egg Lair is he main base of Eggman in Sonic Infinity. Every character gets played here, but a shorter version of the levels (about 1-1.5 mins at average speed).
There are 7 stands that need to be activated in order to get each Chaos Emerald (6 at first) to fall off of the wall in their respective rooms, and they then make each character feel much more empowered.
The 7th emerald is in a secret room that Sonic and Shadow have to get through, and get the seventh emerald in order to launch Sonic, Tails, Knuckles and Shadow's super forms, while having E-199 Chaos and Rouge feel more empowered.
They then go to the top of the ship to have the final battle after it crashes cuz Sonic/Shadow got to the main engine while the other one held Eggman off.
Sonic has to infiltrate a room by running through halls, up walls, dodging bombs and lazers, and getting through waves of enemies. He also must use the Tornado Shoes 3 times. He takes down Eggman's emergency ship.
Tails takes out some army's of ships and then re-retrieves the Tornado for an all-out assault on the bigger one near the end of the levels, and then it turns into he mech and he finds his Emerald. He also takes part in he ending chase sequence in the Tornado to try and get some of Eggman's ships.
Knuckles fights multiple waves of enemies while also platforming. There is one section on top of the ship where the room is located (near Eggman).
Shadow's level play similar to Sonic's but with less bottomless pits and some vehicle sections.
Chaos's level play like they usually do, but they also have a run-away and then chase sequence to get Eggman's robots after they try to escape.
Rouge takes out some robots, sneaks around some, and platforms.