Bowser X is an optional boss that appears in Mario & Luigi: Bowser's Inside Story, its 3DS remake, and Mario & Luigi: Dream Team. This upgraded form of Bowser only appears in the Gauntlet in the Challenge Node and the Battle Ring in Pi'illo Castle respectively.
In Mario & Luigi: Bowser's Inside Story, to get to him, the player must beat all X bosses, and then face all the other X bosses in a row before facing Bowser X. He is the only X boss without a color change from the original and is one of two bosses to not be mentioned in the Prima Games guide, the other being the Shroobs. In Mario & Luigi: Dream Team, he is faced twice: once in normal form alongside Antasma X in his bat form, and again in giant form. He is the second normal X boss faced, and the final giant X boss.
Mario & Luigi: Bowser's Inside Story / Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey
Like all the other X Bosses in the Challenge Node, Bowser X has upgraded stats. He is capable of performing all of the original Bowser's attacks, more specifically from the battle in Toadley Clinic, as well as three new ones based on more abilities Bowser has learned through the game. However, Bowser X only uses two of his Brawl Attacks (unless Bowser did not rescue Shy Guy Squad). The attacks Bowser X performs during battle include:
Mario & Luigi: Dream Team
During the first battle against Bowser X, he is accompanied by Antasma X in his bat form in Class 2 of the regular battle ring. Bowser X uses all the same tactics Bowser does for this battle: He can spew purple waves of fire at Mario before launching a bigger flame attack that Mario must jump over. He can also roll up into his shell and chase Mario through the foreground, creating flames that Mario must avoid while running; the red flames are avoidable by jumping, while the purple ones must be avoided completely. Bowser X will also attempt a sliding punch, which Mario must counter with his hammer; before punching, Bowser X may teleport behind Mario to catch him off guard. Unlike the regular battle where Antasma is forcibly popped out of Bowser and they retreat, Bowser X and Antasma X explode in defeat, possibly due to a lack of story in the Battle Ring, as it's part of the story that Bowser and Antasma escape.
Bowser X is also fought in Giant Class 5 as a giant boss. This fight is mostly the same as its story equivalent. However, his attacks are slightly stronger and faster, and his stats are increased. He also has slightly different attack patterns, and a turn limit of 6 is given.
Mario & Luigi: Bowser's Inside Story
Mario & Luigi: Dream Team
Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey
Names in other languages