Triangulation is a manipulative technique where the toxic person such as a narcissist uses another person to influence the relationship between you and him or her.
One of the things that I recognize very early on in my relationship with the narcissist (the N) that I was dealing with, was how he constantly but discreetly played his exes against me. The N would bring up one of his “favorite” exes on casual conversations, and exclaimed how his ex would do or would not do something for him. He fully expected me to “act” better than his exes by making me compete with them, even though they were not around. This is engineered rivalry.
Another example of triangulation is when the N casually told me he spent time with a member of the opposite sex on multiple occasions and had a great time when I wasn’t around. He insisted there was nothing going on between them. They were “just friends”. He wanted me to be jealous so he could enjoy the extra attention that I would give him. It made him feel more special and further inflated his grandiosity.
Of course, when I questioned him, he said that I was “crazy” or “got too jealous”. That is gas lighting, another manipulative techniques that toxic people use. I find that triangulation is used very frequently with gas lighting to create a double down effect where the victim is manipulated into adopting a certain behavior that pleases the narcissist while at the same time having their own reality distorted.
The person that these toxic people use to triangulate us with also doesn’t have a to be a romantic partner. They can be a family member, a friend, an acquaintance, and sometimes, even their own child if they have children. It’s all about the narcissistic supply, the attention, the praise, the drama that that they can get to satisfy their super ego.