The Soulboost is a battle technique introduced in and unique to the game Custom Robo Arena. It is learned from Stark. According to him, it is only achieved through "a perfect balance of mind, body, and soul." After you give Kris's letter to Stark, the skill is obtained by defeating Stark's students, Shipley and Winchell. By definition, a Soulboost greatly enhances a robo's performance by doubling both the robo's attack and the robo's defense, and temporarily disabling dirt. A Soulboost does not, however, make the robo invincible in any way. The length of the Soulboost is approximately 10-15 seconds. Upon performing a Soulboost, energy rings surround the robo, and the robo's surface becomes the color gold. It is triggered by tapping the touch screen.
It requires a great deal of mental discipline on the part of the commander, not to mention extensive training. Not every commander can perform a Soulboost, and certainly not all can use it to their advantage. Though one should obviously take advantage of the better attack and defense, transforming pauses the battle for a second; this can be used to interrupt an opponent's concentration or breaking their combo. This transformation is only temporary, and once it is finished, the player's robo enters an "exhaust" stage and attains dirt. This leaves the robo vulnerable for a certain amount of time. The cooling down effect is absent on Wi-Fi.
Charging up the Soulboost requires you to battle, and when you battle, the Soulboost Gauge on the lower screen will fill up. Using the Soulboost drains this gauge again. This power has been compared to the "Super Saiyan" transformation from Dragon Ball by some. It benefits truly strong commanders and may be a key turn-around to a satisfying victory.
- There are other purposes to using a Soulboost in addition to the standard reason of gaining double attack and defense. Since the battle is paused for a second to show the Soulboost animation, the opponent can momentarily forget the robo postions, interrupt a combo, or even lose track of their strategy. Advanced commanders often begin moving out of their original position before the animation finishes so that the enemy's advantage is diminished.
- Useful near the end of a filibuster.