Walkthrough
1. Get the GarlicWhen you are in Morgan's house, go upstairs. Open the cupboard and search it. You will get some garlic. Talk with Morgan and ask about how you can kill the vampire and she will tell to you talk with a old friend, hes name is Dr. hallow.
2. Wooden stake
Teleport or go to Varrock. If you don't have the hammer, buy it in the General Store for 1gp, then head to Blue Moon Inn, located in the Southern part of Varrock. To get there, go to the main square on Varrock, then follow the road to the south until you see the pub, which is labeled with a beer icon. Buy some beers before talking to Dr. hallow. Give him some beer and talk to him. Just talk and talk until he gives you a wooden stake.
3. Killing the Vampire
You can now go back to Draynor. But this time, go up to the mansion. Go inside the house, check out the house. Now go down to basement and try to open the coffin there. The vampire will appear and automatically attack you, but kill him. Remember the stuff, and he will be easy. When you have defeated him, the quest is done. Congratulations