In Sonic Forces, several new characters and enemies were introduced, playing key roles in the game's story.

1. Infinite – A major new villain, Infinite, powered by the Phantom Ruby, is pivotal to Dr. Eggman's conquest of the world. Infinite's ability to create powerful illusions and doppelgängers strengthens Eggman's forces significantly, making him a formidable foe for Sonic and his allies.

2. Custom Hero (The Rookie) – Players can create their own character, who becomes an integral part of the resistance, helping to rescue Sonic and ultimately playing a crucial role in defeating Eggman and Infinite.

These new characters significantly drive the plot forward, with Infinite serving as the main antagonist and the Custom Hero symbolizing the rise of new hope in the resistance against Eggman's empire.