In the Prologue of Final Fantasy VII Rebirth, there is one missable element: the ability to Assess the boss of that chapter, Materia Guardian. This assessment is necessary for completing the Enemy Intel, which is a mechanic fundamental to the game.

### Detailed Instructions on Assessing the Materia Guardian

1. **Understand the Concept of Assessing Enemies**:
– Assessing enemies involves equipping the Assess Materia and then using the pertinent command in the menu to reveal the enemy’s stats.

2. **Locate the Assess Materia**:
– You can buy the Assess Materia from the vending machine in Chapter 2, Grasslands, at Bill’s Ranch.

3. **Equip the Assess Materia**:
– Place the Assess Materia in a quickslot so that you can easily use it when encountering new enemies.

4. **Assess the Materia Guardian**:
– During the Prologue, you will encounter the Materia Guardian. To assess this boss, equip the Assess Materia and use the command to reveal its stats. This is crucial because the Materia Guardian is not available for assessment again after the Prologue.

5. **Complete Enemy Intel**:
– Assessing all enemies, including the Materia Guardian, contributes to your Enemy Intel. This is essential for unlocking all VR Missions and other features of the game.

6. **Replay Chapter 1 if Necessary**:
– If you haven’t assessed the Materia Guardian or any other enemies during the Prologue, you might need to replay Chapter 1 to complete this task. However, this is only necessary if you are a completionist player aiming to unlock all content.

In summary, while there are no collectibles or items that carry over from the Prologue to the main game, assessing the Materia Guardian is a critical task that contributes to your overall game progress and completion.