Tarot cards are not okay for fortune telling, Deuteronomy 18:
There was a case of divination in Acts 16:
Paul saw the evil spirit in her and cast it out. This divination and fortune-telling ability was realized by an evil spirit. She had lost that ability:
The last description of casting lots was bright and early in Acts 1:
The next event was the coming of the Holy Spirit on the day of Pentecost in Acts 2. After that, no more casting lots. The Holy Spirit would direct us.
Evil spirits have a limited ability to foresee the future. They could communicate through Tarot cards, Ouija, psychics, etc. When you participate in these kinds of activities, you are drawing evil spirits into your midst.
God sees the entire future perfectly. I rather follow the Holy Spirit and practice
Hearing from God instead of cards.
Is owning tarot cards sinful even if you don’t intend to use them?
I don't think it is sinful but these objects may attract demons. I wouldn't leave them lying around.
What about crystals and gemstones?
They are okay as long as you don't attribute superstitious or supernatural powers to them.