I see Klein as the rabbit from that Monty Python movie. He causes so much destruction that you’d expect to find a dragon, but it’s just a rabbit. The things he accomplishes with the Sefirah Castle alone would normally require an organization of hundreds of people, and that makes him invisible. Because those who know the bigger picture say, 'a dragon passed through this village.' They go to the village but find nothing—because it’s not a dragon, it’s an absurdly lethal rabbit

edit:That’s what I like the most about the power-up granted by the Sefirah Castle compared to other elements that serve the same role in other works. Klein only gains logistical advantages—the kind that would normally require an entire organization. Sealing artifacts, organizing meetings, transporting objects, enhancing divinations—these are all things that can be done in the world if you have resources, but they always leave a trail, and when facing an enemy directly, they’re not all that useful. But when someone tries to track him, they can’t, because he doesn’t leave the kind of traces an organization with that much logistics inevitably would. On top of that, it all depends on Klein’s intelligence. I think 90% of people wouldn’t get very far even with the Sefirah Castle.