The narcissist will bring up the past if it can benefit them in the present moment. They will bring up an event from their past to make themselves seem as though they are greater than you. Or they will bring up an event from your past to make it seem as though you are beneath them. If you have made a fault or mistake in the past, the narcissist will use this to make you feel like you are not as great as you are. It doesn't matter how long ago you made this fault or mistake. The fault or mistake in itself is irrelevant, the narcissist doesn't really care about what you have done. All they care about is displaying some form of superiority over you. If they have to bring up something from your past to do this, they will. They will even share this information with other people to tarnish your image. Narcissists are known to enforce flying monkeys and create smear campaigns. They will even rewrite the past and create their own version of events.
When they rewrite the past, it will always be done in a way where it is favorable for them. They are bringing up your faults or mistakes from the past, because they cannot find anything in the present moment. If you had made a fault or mistake more recently, they would have brought that up. So if they bring something up from many years ago, it's because they can't find anything more recent to use against you. The narcissist will bring up things from your past which could be viewed differently in the present moment. As an example, you may have worn certain clothes or drove a certain car that was fashionable at the time. By bringing up your outfit or car five, ten, twenty years later, it can then be used as a shaming tactic. Narcissists will pull random things from the past to use against you or to shame you, as though they happened yesterday. They do this because in their minds, you are still the same person. They don't realize or understand that people change and people grow. Furthermore, they believe that no matter how many years go by, you are still exactly the same person as you were back then. They believe this because it is true for them. No matter how many years go by, they do not change or grow. They never accept responsibility or accountability for their faults or mistakes. Which means they can never learn from them, and they can never grow. Because of this, they are the same person that they were many years ago.
And they assume that you are the same too, since however they think or feel within, they project on to other people. The narcissist will bring up events from their past to make themselves seem like they are greater than you. It might be something they have accomplished. Something they have achieved or obtained. Whatever it is, it is usually designed to demonstrate to you that they are something of value or significance. They will bring up events from ten, twenty years ago and act like it just happened the day before. They bring up events from their past, because not much has happened more recently. Maybe they don't have anything planned for the future. Some narcissists can be very successful. The reason for this is that they are very good at mirroring people and appealing to their own ideals. You may have noticed this at the beginning of the relationship with the narcissist. They mirrored you and sold themselves to you like they were a product or service. When this strategy is applied to the business world, it can be very powerful and effective. Many people often have a business idol, and they will model their success. The problem is, when the narcissist abandons the character they have created to model the success, everything else goes with it. Just like when they develop a character in relationships. When they get bored with the character, or it is no longer supplying them with what they need, the relationship is over. For this reason, narcissists don't usually experience long-term success.
They frequently hold on to the success they had in the past, and they will bring that up in conversations as a way of displaying their value or significance and getting supply. And you will notice that they do exactly the same thing in relationships. Rather than trying to build on what they have already created with you, they will mention or refer to the beginning of the relationship.
Narcissists will bring up the past as a way of manipulating you into believing that they hold some level of value or significance in the present moment. They will also bring up your past faults or mistakes, as a way of discrediting you or making you appear as less than what you are. Whether they are bring up past events to credit them or to discredit you, it is only because they cannot find anything more recent or in the present moment to use against you.