Yes, there is an enemy that can drop the Emperor White Mask in Metaphor: ReFantazio. The Emperor White Mask can be obtained as a reward from the Rudolf Boss Fight.

Here is a detailed step-by-step guide to obtain the Emperor White Mask:

1. Unlock the Masked Dancer Archetype:
– Ensure that you have unlocked the Masked Dancer Archetype by bonding with Junah. This typically happens when the fifth member joins your squad.

2. Prepare for the Rudolf Boss Fight:
– Make sure you are well-prepared for the fight by equipping appropriate gear and skills.

3. Engage in the Rudolf Boss Fight:
– Locate Rudolf and engage in combat. The fight should be challenging, so use your best strategies and skills.

4. Defeat Rudolf:
– Successfully defeat Rudolf to receive the Emperor White Mask as a reward.

5. Equip the Mask:
– Once you have obtained the Emperor White Mask, you can equip it through Junah’s Accessories slot, allowing you to inherit new skills from other archetypes.

By following these steps, you should be able to obtain and equip the Emperor White Mask in Metaphor: ReFantazio.