Narcissists are chameleons with the ability to appear to be just what you want and need, at least for the initial whirlwind part of the relationship. However, once they have established the relationship, the dynamics change rapidly, with the narcissist utilizing a variety of tactics and manipulations to keep you close. The relationship stops being about creating a partnership and becomes a focus on keeping them happy and their needs fulfilled.
The tactics that narcissists use in this process are easily recognized by those outside the relationship. They may also be evident to the partner, but the myths around narcissism can make it extremely difficult to leave.