I've noticed that quite a few Christians (and Muslims, with the Quran) tend to interpret scripture in the manner which most suits their own beliefs. Any other interpretations are, by their definition, heresy. Handy little philosophy, that.
The Inquisition wasn't limited to Spain. It was just about everywhere the Church was. The Spanish version was just the most notorious. The purging of witches, throughout Europe and America, was a part of that. And in some cultures those kinds of things still go on, though no longer condoned by the Church.As for other Christian ideas not mentioned in the Bible... well, for many years there was a group of Catholics in Spain who were big on bondage and sadomasochism though I am not sure many of the people who suffered at their hands were actually masochists, just heretics who got on the wrong side of Torquemada. Though their justification of 'torture purifying the soul' is somewhat suspect in a modern Christian doctrine...