13 Month Series

The Thirteen Month Series (13월 시리즈, 13 wol shirijeu; or "13 moon series") consists of an Arms Inventory and 12 sentient Ignition Weapons made by a craftsmaster, Ashul Edwaru. They are bestowed by the King Zahard to a formal Princess. In fact, the symbolic significance of the 13 Month Series is greater than any other weapon in the Tower. .

About
It is said that the Thirteen Month Series were made from materials provided by Zahard. These weapons also vary in shape and function. For instance, one is a Needle and another a Hook. Out of these weapons, only the Golden November is the only S-rank. The 12 Ignition Weapons, when Ignited by the user, release vast amounts of power. It is said that only a formal Princess is supposed to be able to ignite a 13 Month Series, though Regulars such as Anak Zahard and Twenty-Fifth Baam have proven this to be untrue.

It is revealed that the thirteen month series together form half of the Key of the Tower that will unlock the floors beyond the 134th Floor. Apparently, the day Zahard announced that he would stop climbing the tower he divided the key into two parts. He gave the first half of the key to the blacksmith Ashul Edwaru. Ashul melted half of the key and turned them into 13 weapons, which Zahard made the princesses fight over them.

No matter how skilled the wielder is, they cannot force a 13 Month Series to Ignite. Depending on the weapon's personality, it may refuse to listen to its owner. Baam managed to ignite Black March, however Yuri Zahard was unable to do the same despite being a formal Princess. When weapons of the 13 Month Series meet, they will resonate and their owners can feel it.

Receiving a 13 Month Series
A Princess who has climbed the Tower and become a Ranker, might be chosen to become a formal Princess who is also called a "chosen Princess". Only a "chosen Princess" is eligible to receive a 13 Month Series, as she has proven her ability by climbing the Tower.

Rules Binding a Princess
When a formal Princess accepts one of the Series, she must abide by a set of rules:
 * 1) She may not give or even lend a 13 Month Series to another person, otherwise they may be viable for execution by Zahard.
 * 2) A Princess may own more than one weapon from the 13 Month Series, such as Yuri Zahard or Garam Zahard.
 * 3) A Princess can refuse a weapon from the 13 Month Series. Heice Zahard, upon becoming a Ranker, was presented with a 13 Month Series but she turned it down for unknown reasons.

List of Weapons & Current Owners
The following consist of a list of the 13 Month Series, along with their previous and current owners.

Notes and Trivia

 * The 13 Month Series all have their names engraved on them. The engraving is in Japanese, because their creator Ashul Edwaru uses a language based on Japanese. SIU made it clear there is no significance behind this, as Chinese, Arabic and other languages are also used throughout this manhwa.
 * The 13 Month Series is actually based on the lunar calendar where all months are based on moons.
 * According to Random Webtoon Fan, the Princess who collects them all would be granted the right to bear Zahard's child. This has been revealed to be their official first purpose.
 * According to Garam Zahard, the 13 Month Series was originally created by Zahard to split the Key of the Tower between himself and his 12 companions. Two would rebel once he decided to stop climbing while the other ten would stay loyal and become the heads of the 10 Great Families.

Navigation
Serie de 13 Meses