Bowser is based on the Chinese Dragon Turtle, a spirit said to bring power, wealth, and fortune. His body resembles a bipedal turtle with a large green shell on his back. His skin is yellow and scaly, with muscular arms and legs that end in sharp claws. His head features sharp teeth, flaming red hair, and two horns. Spiked metal bands cover his arms and neck, and his shell features spikes as well. His size typically varies from being just a little bit taller than a typical human, to being several times taller.
Although Bowser has not been around as long as Mario when it comes to games, he did star as the main antagonist in Mario's first full game and has stuck around since.
Bowser's past is not well known, but at some point he brought his army of Koopas and invaded the Mushroom Kingdom where Mario, Luigi, and Princess Peach lived. Since then he's built a castle at the far end of the land in the volcanic region, and frequently attempts to take over the entire kingdom, usually by kidnapping Peach, although he's taken some more creative approaches as well. Despite usually being the main foe, Bowser and Mario have sometimes shared common enemies, such as the mad scientist Fawful, or the aliens called Shroobs.
Bowser is power-hungry, narcissistic, greedy, lazy, and hot-tempered. He is only out for money, power, and fame. He greatly enjoys fighting, eating, and admiration, though he usually is unwilling to exert himself in anything else unless he gets something out of it. He takes great pride in his fire breath, as well as his castle.
Despite his negative traits, Bowser is known to be very perseverant when he puts his mind to something, and is shown to be a fairly good parent to his children. While not the brightest star in the sky, Bowser is capable of devising plans to work around problems. Additionally, while raiding castles and kidnapping princesses is all in a day's work, Bowser is not shown to be a cruel, underhanded or deranged person, and takes little interest in anything that is not his main focus.
Due to his many defeats at his hands, Bowser hates Mario, and to a lesser extent Luigi and Yoshi, and considers Mario his rival and the only one worth fighting.
Bowser's shown abilities vary a bit among his iterations. He is known for being extremely powerful.
Bowser's signature attack. The Koopa is a skilled fire-breather, capable of letting out numerous fireballs, blue homing fireballs, purple fireballs that pass through walls, massive jets of flame, and a rain of fire. His resistance to fire can vary a bit
Bowser is known to be immensely strong, and surprisingly fast and agile.
He is able to destroy rocks with his fists, lift a ball several times his size, move islands and even create shock waves with the sole force of his leg He can even make incredibly high jumps, similar to Mario and other residents of the mushroom kingdom. In battle, he favors punches and claw swipes as his go-to melee attacks.
Bowser has showed being a skilled user of dark magic (probably by Kamek's education), who can use for teleporting or summoning, shape-shifting, electrokinesis, telekinesis, dark energy manipulation or ￼flight.
Should Bowser suffer death by fire, he can stay alive as a skeletal version of himself. Dry Bowser can reassemble himself if broken, has complete immunity to fire, can throw his own bones at foes, and can still breathe fire. In order to return to flesh and blood, Bowser has to use magic or alchemy.
After suffering defeats, Bowser has been known to grow into a giant version of himself. This is usually done by a third party dousing him with magic, although it was revealed that stimulating Bowser's adrenaline channel when he is in mortal danger can cause him to naturally grow to the size of a castle.
Bowser has had some varying equipment over the years. He typically has been shown to throw hammers, and often has a fleet of airships nearby. He's also had the vacuum block, star rod, spike balls, and barrels. He can even use some of Mario's power-ups like the Super Bell and Double Cherry.