Warning: This blog entry may have spoilers of the game Inotia 3.
When you are on a quest called Twisted Destiny, the Einherjar (silver dragon at dragon’s lair, near Land Scar) will ask you to kill the giant leader named Kenjin, and bring his head to him, in exchange for the rune of abyss.
What you should do is… when facing Kenjin at the land of giants, choose NOT kill him. Just ask if there’s another way of obtaining the rune of abyss. He will give you a drained rune and a fake head of his.
Go back to Einherjar, tell him you brought Kenjin’s head. You will realize that the dragon fooled you. When you talk to the dragon again and prompted for a choice, I suggest that you choose the second option. You will use the rune of abyss on him, and the fight will begin with the dragon’s HP halved. Choosing the first option makes you fight the dragon with full HP. The HP was the only difference I noticed.