The Thirteen Month Series (13월 시리즈, 13 wol shirijeu; or "13 moon series") consists of an Arms Inventory and 12 sentient 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([1],[2]). A member of the RED called Lo Po Bia Ren was sent to retrieve the Green April when it appeared on the 2nd Floor. And later, he was ordered to retrieve the Black March.

The Rainbow Undecimber is the only exception from the 13 Month Series as it is an Arms Inventory, instead of being a weapon.

The 12 sentient weapons are like half-beings and have human forms sealed within. When Ignited by the user, these forms will be unsealed and unleash the extreme powers of the weapon. Only a formal Princess is supposed to be able to ignite a 13 Month Series(Ch 65), though exceptions like Anak Zahard or Baam have proven this to be untrue.

No matter how skilled the Princess is, she cannot force a 13 Month Series to Ignite. Depending on the weapon's personality, it may refuse to listen to its' owner. For example: the Black March will only activate for "Good Looking men" and it won't listen to anyone else. Baam managed to Ignite it, while despite her rank of 500th, Yuri Zahard was unable to Ignite the Black March.

These weapons also vary in shape and function. For instance, one is a Needle and another a Hook. Out of these weapons, only the Gold November has an S-Rank.

When weapons of the 13 Month Series meet, they will resonate and their owners can feel it(Ch 19). It is unclear if the same condition applies to the Rainbow Undecimber.

Receiving a 13 Month SeriesEdit

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"(Ch 32). Only a "chosen Princess" is eligible to receive a 13 Month Series(Ch 32), as she has proven her ability by climbing the Tower.

Rules binding a formal PrincessEdit

When a formal Princess accepts one of the Series, she automatically takes part in a set of rules.

1. She may not give or even lend a 13 Month Series to another person or she will be executed by the King(Ch 2). And it is likely some or most of the people accompanying the Princess will be executed too, for failing to prevent the 13 Month Series from leaving her hands.
2. It is also unknown what punishment is met by the King, when a Princess goes missing with a 13 Month Series.
3. It is possible a Princess may challenge or even kill another Princess for her 13 Month Series but this is currently unconfirmed. It's true the Ha Family is hoping Yuri Zahard will collect all of the 13 Month Series so there may be some truth to this.([3])

Note: Heice Zahard, upon becoming a Ranker, was presented with a 13 Month Series but she turned it down for reasons unknown.

List of Weapons & Current Owners[1] [2]Edit

• Silver January - An Zahard
• White February - Unknown owner > Eurasia Enne Zahard
• Black March (Needle)- Yuri Zahard > Baam > Anak Zahard > Yuri Zahard
• Green April (Hook)- Anak Zahard (Original) > Anak Zahard > Yuri Zahard
• Yellow May - Koon Maschenny Zahard
• Luminous June (Sword) - Alphid Zahard (whereabouts unknown)
• Indigo July - Uram Zahard > Garam Zahard (whereabouts unknown)
• Blue August - Garam Zahard (whereabouts unknown)
• Dark September - Unknown
• Red October (Sword) - Arie Hagipherione Zahard
• Gold November - Adori Zahard
• Colorless December - Eurasia Enne Zahard (sealed)
• Rainbow Undecimber (Arms Inventory) - Never owned

Notes and TriviaEdit

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 has (in his blog) made it clear there is no significance behind this, as Chinese, Arabic and other languages are also used throughout this manhwa([4]).

The 13 Month Series is actually based on the lunar calendar where all months are based on moons.