The Hero Gauge is a gray-framed gauge that appears in the upper right corner on the HUD. Inside it is a blue energy bar and on the left end is a hook.
In gameplay, the Hero Gauge is filled by committing heroic deeds. These include:
- Damaging Black Arms or Dr. Eggman's machinery
- Smashing Black Arms' containers and poisonous plants
- Extinguishing fire sources
- Reviving GUN agents and machinery
- Touching Hero Energy Core items
Once the Hero Gauge is filled, the player transforms into Hero Shadow, which grants infinite ammo for weapons, invulnerability and usage of Chaos Control. However, the Hero Gauge will steadily decrease while Hero Shadow is active and using Chaos Control will deplete it completely. Once the Hero Gauge runs out Shadow reverts back to normal.
Due to the nature of certain missions of some stages, destroying Eggman's factions will only occasionally provide energy for the Hero Gauge.