Just go to your local gaming store and pick up a copy of the dungeons and dragons players handbook. Most everything you need to summon demons and kill your parents will be in there.
Black magic is just the name given to magic intended to harm people, as for witchcraft, find some books, and don't believe everything you read, there's a bit of truth in everything, but nothing is the complete truth.
Personally, I found the Goblet of Fire to contain better spells than the later manuscripts, especially the latest edition of Codex Potterus as Ron Weasly could never pull Emma Watson...
I wonder how you could find out about local traditional Sinagapore magicians or witches. There is a Buddhist tradition of magic; it's strongest in the Tibetan tradition, but I am sure there are strains of magic in Sinagpore somewhere.
I go ogled "Singapore witchcraft" and found this site for you, seems to be a coven in Singapore, you are in luck:
http://www.coven-of-cythrawl.com/coven_of_cythrawl_home.htm
Where can I learn witchcraft or Black Magic in Singapore?
