Karabo Frampton

An Executor of the Holy Church, who boarded the Rail Zeppelin in order to remove his own Mystic Eyes.
He was far too kind a person to be an Executor. Unable to control the Mystic Eyes of Transience, they were only capable of overwriting his own memories with those of another. Even so, his willingness to continue the exhausting work of an Executor despite that is a testament to his superhuman willpower.
Though he was competent as an Executor…he was of course not at a level where he could cross swords with a Servant. As Heartless alluded to in the fight between him and Faker in the Rail Zeppelin case, his loss of his ordinary vision led to a specialization of the Mystic Eyes, and so he didn’t hesitate in letting them steal the entirety of his life force. For him, it was a fight for revenge that he staked his entire life on, one he had to win at all costs for the sake of the children he would protect. And he won.
The Mystic Eyes of Transience are Jewel Class Mystic Eyes.
Thinking of something to serve as the "eyecatcher" for the Rail Zeppelin, I thought that if Mystic Eyes of Death Perception are a type of future sight, then what would be the ultimate extreme of hindsight? The result was, as seen in the story, the ability to draw forth anything perceived in the past. That attack was something that couldn’t be protected against by any physical or magical means. It didn’t care about Noble Phantasms or Personal Skills. An anomaly that couldn’t be prevented except by interfering with cause and effect itself.
In addition, the idea of time being visible as bubbles is an approach to time being considered by modern science now.

Lord El-Melloi II Case Files material: Lord El-Melloi II Case Files Glossary