The two weapons
Midway through the book, it is revealed that the two weapons,
Heaven Sword and Dragon Saber, are actually made from a single
sword, Xuan-Tie-Jian, which Yang Guo wielded in the prequel (set
nearly 100 years ago), The Return of the Condor Heroes. The great
sword belonged to Dugu Qiu Bai, a great martial arts hero whose
skills were unmatched under the heavens. Yang Guo came upon the
sword while he was recovering from the loveless poison and the loss
of his arm.
Later, when Yang Guo and his master/wife, Xiaolongnü left
Xiangyang, he left the sword with Guo Jing and Huang Rong. It was
said that the sword was melted, special steel material was added
and made into the Heaven Sword and the Dragon Sabre. Hidden within
the Dragon Sabre was the military textbook (Wu Mu Yi Shu) written
by the late great Sung Dynasty general Yue Fei; similarly,
hidden within the Heaven Sword was a scroll detailing the powerful
martial art Jiu-Yin-Zhen-Jing and (legends told that Guo Jing wrote
the Dragon Subduing Palms or Xiang Long Shi Ba Zhang manual along
with Jiu-Yin-Zhen-Jing). The former was given to
Guo Jing and Huang Rong's son while the latter was
bestowed upon their youngest daughter, Guo Xiang who was Yang Guo's
favorite and founder of the Emei Sect.
The content of the hidden book and scroll, plus the fact that the
two weapons can only be broken (thereby revealing said book and
scroll) when used against each other, was the source of the claim
that whoever possessed the sword will be "untouchable" and whoever
possessed the sabre will rule "all under heaven".
The secret of the weapons was passed down via (and only through)
the leaders of the Emei Sect. Zhou Ziruo was the latest leader of
the sect, and about half-way into the novel, she managed to obtain
the two weapons through her scheming and deception.
The two weapons analogy: In the Chinese culture, the dragon
is considered a king, which probably why many of the TV adaptions
gave the sabre a golden-copper color. The Dragon Slaying Sabre
means to kill the king (which in this case is the Mongolian
ruler). However, dragons can get out of control and become
tyrants. The Heavenly Sword is Heaven. Only Heaven is the true and
only authority in choosing a ruler and dethroning him. At the end,
the Dragon Slaying Sabre is destroyed by the Power of Heaven.
Woow, i didnt know these. 
