The addition of the letter "k" to the word "magic" is often associated with the practice of ceremonial magic, which has its roots in ancient Egyptian and Greek practices, and later became popularized in the Western esoteric tradition. The use of the "k" is meant to distinguish this type of magic from stage magic or illusions.
In regards to Christianity, it is true that some sects of Christianity may view magic as sacrilegious. However, there are also many Christian traditions that incorporate magical practices, such as prayer and ritual, into their beliefs and practices.
Ultimately, the validity of magic is a subjective matter and depends on one's personal beliefs and experiences. It's important to avoid making dismissive and judgmental comments about topics that one may not fully understand.