The Soul Gauge is a game mechanic that appears in the Sonic Storybook Series. The Soul Gauge allows the player to store energy needed to perform special moves in gameplay.
Sonic and the Secret Rings
In Sonic and the Secret Rings, the Soul Gauge is presented as a golden gauge on the right side of the screen, where the charged energy is represented as a burning orange/blue bar inside it. In this game, it is a Skill that is obtained after clearing the Mission "Go for the Goal" in Evil Foundry and costs 10 Skill Points to be equipped. If not equipped, the Soul Gauge will not appear in or be a part of the gameplay.
The player can charge up the Soul Gauge by collecting Pearls and defeating enemies. However, there are also Skills that, when equipped, allows the player to charge or grant additional energy to the Soul Gauge when certain conditions are met. Also, in battle against Alf-Layla-wa-Layla, the player can only fill the Soul Gauge by shaking the Wii Remote. The amount of energy that the Soul Gauge can carry increases as the player increases in level, increasing every five levels. It starts with a capacity of 100 and increases to 300 at maximum at about level 50.
In the game, the Soul Gauge is used to perform Speed Break and Time Break; Speed Break lets Sonic go at a high speed to blast through obstacles and past certain hazards, and Time Break slows down all enemies and movements in the area. In order to perform these actions, the Soul Gauge must have been charge with enough energy to reach the burning point (where the color turns from blue to orange). The energy in the Soul Gauge will decrease whenever these actions are used.
Sonic and the Black Knight
In Sonic and the Black Knight, the presented as a bar with a kite shield on the left end in the lower left corner of the screen, where the charged energy, called Soul Energy, is represented as a red bar inside it. In this game, it is an integrated part of the gameplay, meaning it is always active.
The Soul Gauge can be charged up by collecting red fairies, attacking enemies, or by performing certain actions based on the chosen Combat Style. There are also Skills that allows the player to gain additional Soul Energy to the Soul Gauge when certain conditions are met. Also, in the battle against the Dark Queen, the player can only fill the Soul Gauge by countering each of the Dark Queen's sword swings. The amount of Soul Energy the Soul Gauge can carry remains the same throughout the game. Taking damage deceases the Soul Gauge.
In the game, the Soul Gauge is used to perform Soul Surge, which let the player perform a special attack that can be used to attacks targets, launch a kick or give an increase in speed (the two latter can only be done in Adventure Mode). In order to use Soul Surge, the player must have some Soul Energy in the Soul Gauge. The gathered Soul Energy will decrease whenever the Soul Surge is used.