Episode Shadow - Sonic Forces Guide - IGN

Outside of the main story missions in Sonic Forces, Episode Shadow is additional story content that is a prequel to the main missions. The three stages are

Sonic Forces Walkthrough - Eggman Boss Battle - IGN

Sonic Prime - Rotten Tomatoes

Wispon, Sonic Wiki Zone

Shadow the Hedgehog - Sonic Retro

Sonic Forces - IGN

Mystic Jungle - Eggman's Facility - Sonic Forces Guide - IGN

Doctor Eggman Sonic News Network+BreezeWiki

Rouge the Bat/Miscellaneous, Sonic Wiki Zone

Sonic Forces [Trailers] - IGN

Sonic Forces - IGN