The Tower
"The Tower" is a mysterious structure that is completely enclosed and hosts many unique environments. It is permeated by an element called "Shinsu", which has strange properties similar to magic in other comic universes. It is inhabited by many different intelligent species. Living on the top floors is associated with a higher status in the Tower and better living conditions. This is because ascension from one floor to the next is only allowed by passing increasingly difficult tests of strength, dexterity and wit. Regulars are any individuals from the Outer Tower chosen to climb the tower in the Inner Tower. Former Regulars who reach the top of the Tower are known as Rankers, and are generally much more powerful than others. Rankers are often put to work administering the lower floors. At the top of the Tower sit the "Ten Great Families", which form the governing body of the Tower. A figure known as King Jahad (or 'Zahard', in some translations) is the chief leader of this body.
Each floor is composed of three layers: an external Outer Tower which serves as the residential area, an Inner Tower where people are tested, and a Middle Area, which acts as a network linking each floor. Residents of each floor are given the chance to ascend, provided that they are deemed "worthy" of doing so by Headon, the First Floor's Guardian and caretaker of the Tower. Such people are referred to as "Chosen Regulars" in Tower of God. The Tower is sealed from the vast, unknown "Outside" by portentous, impenetrable doors. On rare occasions, extraordinary people are able to open the doors and enter the Tower. Such people are called "Irregulars" in the manhwa, and Twenty-Fifth Bam is one of them.
According to the author, each floor is the size of the North American continent. Each floor often has its own culture, language and governance systems, and it is not uncommon to have nations living in isolation and unaware of the existence of the tower.
Only Irregulars are exempt from the contract Jahad struck with the Tower Guardians that made him immortal. Thus, only an Irregular can kill Jahad. This fact drives much of the plot in Tower of God.
Shinsu
Shinsu, roughly translated as "Divine Water", is a substance found within the Tower in varying concentrations on each floor. On the lower floors, Shinsu is diffuse and inconspicuous, similar to air. However, on higher floors, Shinsu increases in power and concentration, and is said to be viscous and flowing similarly to water. High Shinsu resistance is required to enter these floors. Residents in the tower must form a contract with the "guardian" of the respective floors in order to manipulate Shinsu.
Shinsu can be manipulated to enhance physical abilities, powerful weapons, and even manipulate the elements. Bang (Korean-방) is the number of discrete units of Shinsu control. The more Bangs someone handle, the better the ability to control shinsu. The size of the units is called Myeon (Korean-면), and the concentration is called Soo (Korean-수). Though used with varying degrees of explicitness and even conscious awareness, its use seems to be inextricable from combat within the Tower. Shinsu reinforcement (Korean-신수강화-shinsooganghwa) is a technique used to strengthen the body, and is commonly used by Regulars. Those who are strong with Shinsu have their aging slowed to the point where they become effectively immortal. It is unclear to what extent aging is slowed simply by living in the tower without training to use Shinsu.
Shinsu does not have a fixed flow, but there is a temporary flow. Using this flow to attack is called flow control. Expert wave controllers could destroy a village with this. Reverse flow control is used to strike back in the direction of the flow and to stop the opponent. Sometimes they are used simultaneously, attacking with flow control and protecting the body with reverse flow control. Flow control is a favored technique of Twenty-Fifth Bam.
However, there are certain exceptions to rules regarding Shinsu. Individuals known as "Irregulars" seem to have a special connection with the tower, being able to use Shinsu with little to no constraints, regardless of whether or not they have contracts with the same administrators of the floors they're on or going to. One highly notable irregular known simply as "Enryu" even managed to kill the then administrator and guardian of the 43rd floor.
Positions
Most battles in the tower are done in teams. Each person in a team plays a certain role in battle, which are referred to as positions. There are five basic positions: fisherman (낚시꾼 nakksiggun), spear-bearer (창지기 changjigi), light-bearer (등대지기 deungdaejigi), scout (탐색꾼 tamsaekggun), and wave-controller (파도잡이 padojabi). Fishermen are direct fighters, spear-bearers are a fighting support class, light-bearers provide distant reconnaissance, scouts provide on-ground reconnaissance, and wave-controllers control Shinsu. There are other positions, such as guide, but they are rare.
