The term 'treacherous sort' can be described by two crossword solutions: SNAKE (5 letters) and SERPENT (7 letters). Snakes and serpents are both members of the suborder Serpentes, which is a group of reptiles that have long, limbless bodies and typically live on land. They are known for their predatory behavior and often have venomous bites. Snakes and serpents are considered to be treacherous creatures due to their ability to surprise and harm unsuspecting victims.