They were impressive. They told you stories of impressive performance in business and incredible success in general. Their air of confidence convinced you the stories must be true, even though you didn't see anything to verify this. Sure, they drove a crappy car but that is because they really loved that model, not because they didn't have the money to buy a new one.

They manipulated your sympathy. At the start, they had a story about a hard childhood, a bunny-boiling ex, a recovery from cancer, or something else designed to elicit sympathy in you. It was probably short on verifiable detail and unlikely to be true. The purpose was to gain your pity and attachment. We are much less judgmental about people we feel sorry for and much more likely to reveal our vulnerabilities to them.

They surround themselves with fans. Once you are hooked, they will start keeping company with other people – new potential partners. This is to remind you that you are lucky to have them and that they have plenty of other options. As a result, you feel constant anxiety about your relationship.

They have no past. You will rarely be introduced to anyone who knows them from before you met. These people will not give good reviews, so you are kept away from them.

They will sabotage and sever your relationships. They will work hard to cut you off from your friends and family. They will work to make you feel uncomfortable around the people you used to feel most comfortable with. They want you to be dependent and loyal only to them. They do not want other people telling you your partner is a nutbag. They are jealous and they will actively exclude potential partners from your life.