What is a Nightfall Memento in Destiny 2?

A Nightfall Memento is a customization item dropped exclusively upon completion of a GM Nightfall. When you insert the memento into your legendary gun, you unlock various features for the weapon, such as the Triumphant Keepsake shader, a tracker, and a title. The shader’s main component is an orange texture that gives your gun an unusual look. Some weapons look better with the shader than the others. Before inserting the memento, you can preview how your gun will look with the applied shader.

Why is it hard to obtain Nightfall Mementos in D2?

The source of acquisition for Nightfall Mementos is Grandmaster Nightfall strikes, which cranks up the difficulty. A GM strike is an unforgiving activity with plenty of dangers, including strong Champions, increased enemy damage, limited resurrections, and more. Here are the main reasons why it might be hard to obtain Nightfall Mementos in GM Strike:

• Champions and overall difficulty. Grandmaster is truly an end-game activity, because it tests your build and knowledge of the game like nothing else. During a GM strike, you usually meet plenty of champions that deal significant damage and can only be stunned through special effects. Those guys must be dealt with fast, so they won’t cause trouble;
• Instant wipe mechanic. If all three guardians die during a GM strike, they go to Orbit. They don’t get any rewards and must restart the mission, which consumes time and can be annoying. It’s recommended to be cautious during the activity, especially when one or two guardians are down;
• Stress test for your build. If your build has weak points, a GM strike will expose them to you. So, you'd better prepare it before heading into the mission. The preparation includes obtaining weapons with strong perks, armor with the right stats, finding an exotic that suits your playstyle, and more.