Is the word 'slave' only presents: the one who is owned by another person and is forced to work for them... or, can this word be used for 'someone who is sincerely devoted to someone, for example an ancestor or a teacher? 'A' believes 'B' to be his master and is sincerely devoted to 'B', can 'A' say? I am a slave of B.
At least in American English, due to our history, the use of the word slave is considered very offensive. To call anyone your slave conveys a message they that are below you and owned by you. The words apprentice, servant, or student have a more positive connotation in my experience. I would avoid calling someone a slave.