According this book, Shiva promised Daksha to save the

According
to Hindu mythology, Lord Shiva is the Destroyer
and the most important God in the Holy Trinity, the other two being Brahma the
Creator and Vishnu the Protector. Lord Shiva is no ordinary god; he is
very mysterious and some myths believed that Shiva as a normal human being
and  later turned into god. Though people
believed, Lord Shiva is the ferocious god, but he has another mysterious side
as a normal being and famous for meditation.  The way of  looking from several angles, we are always
struck with the nature of Shiva. In the view of a normal human being, people
believed him as a warrior and it is  reflected in the Amish’s The Shiva Trilogy. It consists into  three books, called ‘The Immortals of Meluha’, ‘The Secret of the Nagas’, and ‘The Oath of the Vayuputras’. The story
is about the normal side of Shiva as a warrior later turned into legend then
God. It is an adventurous story that happened before the centuries. Today
people remembers him as Mahdadev, Gods of Gods. In this book, Shiva
promised  Daksha to save the land from
enemies. Shiva and his tribe are impressed with the Meluhan way of life. He
comes to know that the princess of Meluha, ordained to a life of
loneliness as she is a Vikrama . He decides to
marry Sati, and broke the law of the city. Once,  the inventor Brahaspati invites them to Mount
Mandar, where the Somras is manufactured, with the help of Saraswati river. Through
this story, we can understand that the potion did not affect him but his throat
was turned into blue. Meanwhile, Shiva will lead the Suyavanshis to
victory against their arch rivals Chanravanshis who have stooped low enough to
even recruit the brutal, evil assassins – the Nagas. Unfortunately,  Sati is attacked by
a Naga and the gold coin that leads Shiva to Branga.  In the 3rd book, he meets the chief of Vayuputras, 
Mithra who convinces the Vayuputras that Shiva is the real Neelkanth and
gives him the Pashupathiastra which
acts on a specific target, rather than annihilating everything like the
Brahmastra. Thus, The war ends with Sati’s death, Shiva unleashes the astra and ends Devagiri’s history, along
with the Somras manufacturing units hidden beneath the city. Shiva retires to Mount Kailash where
he lives the rest of his days peacefully,
 though missing Sati every day. Sati’s death is not forgotten and she is later renowned as
Goddess Shakti. Creation
and destruction are the two ends of the same moment. The creation and the  destruction is the circle  of life. However,  Shiva
Trilogy is a philosophical fiction.