Negative thoughts as mentioned in Agi Yoga

Observe how people read the Teaching. Observe which passages they avoid and try not to notice. People especially often close their eyes to everything referring to betrayal and psychic murder. They do not even wish to consider that they can harm at a distance by their thoughts. Thus people avoid that in which they are most often guilty. One does not have to be a giant of thought in order to harm. Even a mediocre thought poisoned by the crystal of imperil will be very effective.
-Master Morya through Helena Roerich, Heirarchy