What is Dragon Nest manga about ?

Based on Massively Multiplayer Online Game (MMOG). The beautiful Goddess Altea, creator of the tranquil worlds of Lagendia, plummeted into unconsciousness after being poisoned by her jealous, evil sister Vestinel. The poison can only be neutralized by an antidote made from the source of the poison itself - Vestinel's magic grail - which has disappeared into Lagendia along with sinister Vestinel herself. Able to communicate to her people only through dreams, the Goddess Altea calls upon the Heroes of Lagendia, via all-knowing prophets, to find the grail and save her from her eternal slumber. In their quest, the bold warriors must comb the lands for enchanged Power Stones, which allow them to speak with the prophets and unlock the will of Altea through her dreams. But the hunt for the Power Stones is not for the meek, as since the Goddess Altea's poisoning, the formerly peaceful lands of Lagendia have become home to throngs of deadly dragons bent on thwarting the grail's discovery and keeping the land in despair.