Baam is a young boy with brown hair and amber/gold eyes. He wears a brown long sleeved shirt, red vest and beige pants. After the Crown Game test he received a lowest tier regular uniform and a hairband from Koon.
He is described as good looking and cute by the Black March and Androssi . He is overall human-looking.
He was named after his birthdate - twenty-fifth night. Later, the Guardian of the 1st floor, Headon, abbreviates his name to Baam, joking, "It has become a tasty name!' In Korean, the word 'baam' has two meanings: one is 'night' and the other 'chestnut'.
Baam's early life is mostly unknown and nothing is known about where he lived before coming into the Inner Tower, other than that it was some kind of cave. He was dressed in an unkempt manner, had long unruly hair, and a white scarf around his neck. There was only one source of light in the cave, towards which Baam built a huge tower of stones. After climbing his tower, Baam found the light was unreachable, shining through a crack in the high cave ceiling. This caused him great upset, but as this happened the rock above broke off, and a girl with it, Rachel.
Rachel became Baam's only friend, and taught him how to read, write and talk. She also told him about the sky and stars, and of human warmth. She educated him on many things about the human world, though his grasp on human society is still fairly poor.
The two played a crude board game in the cave with chalk lines and stone pieces, always drawn out somehow by Baam's tactics. Rachel would frequently journey above through the opening from which light cascaded, denying Baam to come with her, telling him, "Up there, only those who have been chosen can play." She told him stories of the world above; of the yearly festivals, the fruit-bearing trees given by God, the children playing - a world filled with light and merriment. Baam would wait for her to return with nothing else to do but dream of going up there and playing with her.
Baam enters the Inner Tower in search of his friend Rachel. When Rachel decided to climb the Tower, a golden light descended on Rachel to take her away, but when Baam grabbed her, he was also caught in the light and separated from her.
Baam awakens on the First Floor of the Tower where he encounters Headon, the Guardian of the 1st floor. Headon welcomes Baam and decides to test him with a Ball test, in a chamber guarded by a White Steel Eel, telling Baam that he can go to the next floor if he pops the Ball. At this same time, Yuri Zahard hears that an Irregular has entered the Tower, and travels down to the bottom floor alongside Evan Edrok. Evan gives Baam a Pocket, as is customary for arrivals into the Tower, but he receives an expensive A-Grade model. Yuri warns Headon that the test is too difficult for Baam but Headon refuses to change the test. However, he does agree to bend the rules to allow Yuri to lend Baam her weapon, the Black March, to help him pass the test.
Baam manages to get past the White Steel Eel by letting it swallow him and then stabbing it in the tongue. Consequently, he gets to the Ball and punctures it with the Black March. However, the Ball does not pop, so Baam listens to Evan's advice to call out to the Black March, asking it to ignite. To Yuri's surprise, the Black March listens to Baam and bursts the ball, sending Baam to the next floor.
He arrives on the 2nd floor in a grassy plain and is immediately engaged in a survival test to cut down half of the participants in the area by any means. He is attacked by a Regular, but manages to escape due to luck and considerable agility. He decides that he has to fight if he wants to ascend the tower and find Rachel, and is just about to attack a harmless creature when Koon appears and tells Baam he is making a mistake. Rak then appears, wishing to "hunt" Baam and the Black March in his possession. Koon then launches a surprise attack on Rak, giving him and Baam time to hide behind a rock from the infuriated hunter.
An announcement calls, ordering the Regulars to team up in groups of three, thus leaving Baam and Koon no choice but to try and group with Rak. When persuasion fails, Baam attempts to confound Rak by dropping the Black March and asking Rak to continue hunting him. Baam and Koon seize this opportunity to grab Rak at the last second, forcing him to team up with them, admitting them to the next phase of the test.
The survivors are teleported to a room to meet their Exam Supervisor, Leo-Ro, who blasts a Shinsoo barrier at them, stating that whoever passes through it passes into the next test. The barrier appears to have little to no effect on Baam, and so he immediately passes, much to Lero-ro's surprise. The examiner sits down with Baam and wagers a bet on who will get through the barrier first, with the prize of the winner allowing to ask the loser a question. Both bet correctly but despite the draw, Lero-Ro allows Baam to ask what an irregular is, which Leo duly explains. Afterwards, Koon and Rak emerge through the barrier, readying the team for the next test.
Baam, Koon, and Rak are presented with the examiner Yu Han Sung's test, in which they have to rely on a scant few clues to choose a correct door out of several, and pass due to Rak kicking open a random door within the time limit. They then decide to take part in a bonus test called 'Crown Game', the winner of which instantly passes onto the 3rd floor. The team set off in the 2nd round as the Black March reacts to the ignition of Anak's weapon, Green April, which is noticed by her. She demands that he give it to her, coming off the throne and so forfeiting the game. Baam makes a bet with Anak to give Black March to her if his team fails to win the next three rounds, but if he wins then she has to give him Green April. Baam's team manage to take control of the throne and Baam sits on it with the crown while Koon, Rak and their allies fend off the other Regulars. This stance is maintained until the final round, when a mysterious cloaked team enter the contest, one of which Baam becomes convinced of being Rachel. She is subsequently attacked in front of him by a masked combatant, later revealed to be Hwa Ryun, and so he instantly surrenders the throne and game to save her, subconsciously activating his potential for Shinsoo. The Shinsoo attacks Hwa Ryun, slicing her mask and face, and both fall to the ground unconscious. As a result, he loses the Black March to Anak.
Baam wakes up five days later, two days after the Position test has began. Koon tells him that the girl he saved was not Rachel, although Baam is still convinced and wonders why Rachel did not simply tell him the truth. He is assigned the Wave Controller position and discovers that he has an incredible talent for handling Shinsoo in his studies. He befriends with some of his peers during this stage, including Androssi, Hatsu, Ho, and Ship Leesoo.
In the last stage of the Position test, the Hide-and-Seek game, Baam is assigned to Team B. He watches Team A's attempt through a monitor and is saddened by Koon's loss.
As Team B enter the game, Baam travels with the teams' fishermen Androssi, Des Lion and Hong Chunhwa. He talks with Androssi about her history, and wonders how she managed to get all the food she wanted. Androssi then assaults her fellow Fishermen, making Baam realize how she had done it: by defeating or killing everyone who got in her way. Des Lion then attacks Baam, believing him to be in on Androssi's plan but Androssi steps between them and suppresses the strike. She tells Baam to watch closely as she was going to show him what is necessary to climb the Tower and protect Rachel, and starts towards Des Lion. Baam comes between them to stop the fighting, only to be betrayed by Lion who takes him hostage. However, he is easily despatched and slammed against the far wall, causing Hong to ignite his blade, Namaruda, firing a surge of Shinsoo at Androssi. Baam again gets in the way and takes the impact head on, managing to stay standing. He decides to leave them, as he would not fight others, and would never attack those precious to him, even if it got him to the stars. Androssi asks him why he keeps chasing Rachel, and he simply replies, "The heart moves where the heart wills," and runs off.
He then finds a Lighthouse, and its controller tells him that they have lost communication with Rachel, who was within the Safety Zone. Baam heads over there in fear of her safety. When he arrives, he finds Ho holding Rachel with a knife to her neck. She threatens to kill her unless Baam defeats Quant. Quant subsequently engages in combat with Baam and immobilizes him with Shinsoo. He whispers to Baam that if he can copy the Paralyzing Flow he used on him, he could stop Ho for long enough to rescue Rachel. Baam does this with relative ease, and saves Rachel.
As Androssi emerges on the scene, Baam utilises his newly acquired paralysis ability to help her successfully defeat Quant.
Afterwards, it is discovered that Rachel has lost the use of her legs, and so Baam asks Koon and Rak for help in enabling her to carry on up the Tower. Later that day Baam finds out that he has passed the Position test. It is found out that in order for Rachel to continue ascending the Tower, an Irregular would have to consult with the floors' Guardians, and so Baam admits to the congregation that he is one. After the results, all the participants who pass decide to side with Baam in his route up the Tower via Guardian-directed testing, despite the implications of helping an Irregular.
In the standby before the final exam on the 2nd floor, Baam attends Ho's funeral and trains in hand-to-hand combat with Androssi.
The final exam, the Submerged Fish Hunt, involves Baam being encased within a large bubble alongside Rachel. In the aquatic environment, Baam feels strangely envigorated and empowered. As the timer on his Pocket indicates 13 minutes left, Baam talks to Rachel about her legs and their ascension up the Tower. Presented with the question of why she wants to see the stars, Baam realises he does not know the answer. He reveals his happiness at being beside her again and how he has changed since he last saw her.
As the two talk, they are interrupted by a dark projectile from the depths beyond that glances the bubble containing them, and are astonished to see that the Bull has found them. As it approaches to devour them with its jaw stretched out wide, Baam summons all his Shinsoo into one blast. This freezes the Bull in place, allowing the bubble to drift on past it. The bull starts moving again, but Baam quickly kills it. As the Queen Whale appears, Baam goes to share his happy victory with Rachel, until she unnexpectedly stands up, with no trouble, and pushes Baam out of the bubble, saying; "I'm sorry Baam. Here, you need to die."
It is hinted he is still alive when Hwa Ryun states she would go to see the "Night that lost the stars."
Rachel: Baam has a deep friendship with and has strongly implied he is in love with Rachel. She was the reason he had entered the tower in the first place. However, since Rachel requested Koon to lie about her identity, Baam wonders why she will not just reveal herself to him, and is aware she may not want him to follow her, but has decided to do so anyway.
Koon: Baam was a little uneasy with Koon at first, but they are now fast friends, despite being character foils. Koon has in fact helped Baam out more times than he knows...
Rak: Baam is also friends with Rak, although he is a little bit annoyed by him at times.
Being an Irregular, most think he would be incredibly strong, however at the start of the series, this is not apparent. But later in the story, Baam is shown to be a prodigy at manipulating Shinsoo. He learns techniqes that most Rankers take decades to learn, in mere seconds. It can be considered that he is even stronger than Androssi now, as he managed to kill the Bull, a feat which even Anak and Androssi couldn't pull off.
Agility: Baam is very agile; he can dodge sword blows very effectively. After his training with Androssi he has gotten much faster and can even avoid the fastest attacks.
Intuition: Despite not being much of a fighter, Baam has good fighting instincts, as shown when he correctly determines a Steel Eel's weakness in only a few seconds.
Novice Shinsoo Genius: Baam can use Shinsoo surprisingly well for someone who has had little experience or training with it. For example, he learns the Paralyzing Flow technique within a few seconds and rapidly becomes able to use it at a reasonable range, which Quant reveals took him decades to learn. So, logically, he can be considered to be stronger than a Ranker when it comes to Shinsoo. Presented with the scenario of protecting Rachel, Baam's potential far exceeds the norm, and in one instance it appeared the Shinsoo around him struck the enemy Hwa Ryun of its own accord. He is also able to use Shinsoo without having formed a contract with the current floor's guardian -- something that is considered both impossible and against the very laws of the tower.
ShinsooBeams: Baam can fire beams of Shinsoo, the largest seen so far was big enough to puch straight through the Bull's head.
Paralyzing Flow: At medium to close range, Baam can temporarily immobilize an enemy using Shinsoo. This is an ability taught by Quant that usually takes decades to learn which he mastered instantly, and apparently Baam can use it at a greater range than most.
Shinsoo Resistance: Normally, a person wouldn't be able to move under enormous density of shinsoo, which is usually located at where the white steel eels live. However, Baam has demonstrated an amazing resistance to shinsoo pressure, being able to move freely even in dense shinsoo environment. This is also shown during Leo-ro's test when Baam was unaffected by the shinsoo barrier that Leo-ro casted, while all the participating regulars were moved back. He was blasted by a powerful wave of Shinsoo as Hong Chunhwa's weapon, Narumada ignited and emerged relatively unscathed by the attack.