Fairy Castle Cactus is the other name of Acanthocereus tetragonus which is a very easy to grow indoor cactus plant
Like most cacti plants the fairy cactus are fairly low-maintenance and hardy. Make sure they receive enough water without becoming waterlogged, especially during the summer, and fertilize them for best results. If the roots have become black or overly soft, the cactus could be experiencing root rot – cut away the affected parts and replant. Well-drained potting soil is best, and most of these plants grow well in a soil that contains good compost material.
This plant can be used in terrarium decorations
Note: The plant shown in the pic is a live plant and may differ from the plant that is being shipped.