Bass makes his debut when Zero Two and the Dark Matter invade the Smash Bros. Galaxy, where he has Zombie Iron Man fly up towards the heart of the Dark Matter so he can use a Footstool Jump to get to Zero Two. Bass is then able to injure Zero Two, forcing him to flee.
Bass makes the transition to the side of good during Mechtavius Destroyer's siege. Initially fighting alongside the other villains, as the heroes are on the verge of victory, Bass decides to switch sides, much to Dr. Wily's anger.
At the start of the Coin Festival, Bass comes to the aide of the Heroes of Legend after they are ambushed by Ridley. Bass then proceeds to pursue Ridley after he flees. Later, when the League of Villains attempt to recruit Rosalina to their side, Bass and E-123 Omega fight alongside the Heroes of Legend. However, Bass makes it clear that he isn't doing it out of the kindness of his heart, as he brutally attacks the already damaged Mecha Sally. Bass later flees when the Children of the Gods attack, but returns during the conflict against Dr. Eggman to prove he is the strongest robot in existence. Despite this, Bass is unable to defeat Dr. Eggman.
In Season 33, Bass is seen attacking the remnants of Bowser's forces, presumably as a form of training when he is confronted by Marth. When Marth tells Bass that he has no reason to be so violent since Master Hand is gone, Bass states that even in times of peace, he can never let his guard down. After Marth leaves, Bass notices raw Phazon in front of him, which confuses Bass at first because Earth has never had contact with raw Phazon. However, Bass then sees Dark Samus nearby, and learns that she placed the Phazon there to get his attention. Bass then learns that ever since Master Hand's defeat, the League of Villains have been unable to harvest Phazon for Dark Samus since they can't gain access to Phaaze. While Bass could care less about the League of Villains' harvesting of Phazon, he realizes Sonic the Hedgehog hasn't returned yet, and realizes the Earth could possibly be in danger. Bass then leaves to find the Heroes of Legend, aware that they can avert a crisis like this. Upon finding the Heroes of Legend, Bass explains the situation to them, and how he heard a voice on the way to them. Bass is then put under observation by Mario, Luigi, and Samus Aran, but later goes beserk due to the Phazon he touched earlier infecting his body, prompting Shadow to extract it from him. Bass is left exhausted by this, but remains conscious. Bass then learns of Shadow's desire to keep his promise to Maria. After Goku teleports Shadow to Phaaze, Bass asks the Heroes of Legend why they fight for a peace that doesn't last long, and is told by Metal Sonic that they are also doing this for Sonic. Bass then learns why Metal Sonic betrayed his creator. Bass then reveals the reason he was created was to defeat Mega Man. Bass also explains that he betrayed Dr. Wily because he felt that Dr. Wily was holding him back because he keeps reviving his Robot Masters. Bass states that he wanted to fight against foes like the ones the Heroes of Legend fought, because he felt that if he could beat someone who had the power of the gods, then he knew he could beat Mega Man. However, despite his determination, Bass could never beat the foes the Heroes of Legend go up against, which frustrates him. Bass is then offered a position in the Heroes of Legend by Metal Sonic, who sympathizes with Bass because he used to be just like him, and wants to train Bass personally to help him get stronger. Realizing the opprotunity he has in front of him, Bass accepts Metal Sonic's offer and joins the Heroes of Legend.
Bass is arrogant and full of pride. Bass does not care about peace or the greater good, he only desires to prove he is the strongest, as every battle he has been in was to prove his strength.
Bass' goal is defeat Mega Man, which is what he was created to do. The main reason Bass betrayed Dr. Wily was because he felt that Wily was holding him back from fighting foes like the Heroes of Legend have fought, because Bass feels that if he can beat someone with the power of the gods, then he will ultimately manage to defeat Mega Man.
Bass refuses to tolerate cowardice, as he personally pursued Ridley after he fled. Bass will not hesitate to go all out in battle, as he brutally attacked Mecha Sally even though she was already damaged severely by Rosalina. Despite this, Bass is able to prioritize his goals, as he went to find the Heroes of Legend after learning about the League of Villains' loss of access to Phaaze, not because they harvested Phazon, but because it happened after Master Hand's defeat, due to the potential threat the situation posed.
- Bass is the second inorganic Hero of Legend after Metal Sonic.