Every guide had their own way to visualize an esper's corrosion. Some saw it like a billowing smoke, and visualize their guiding like an exhaust that sucked the smoke away. Some use a rusty sword as a visual and imagined themselves chipping at the rust. It was one of the first lesson guides would receive on their training course.
But Zein never received a proper training course.
Zein didn't see the corrosion inside the esper through analogical visualization. He looked straight into the root of an esper's system; their mana core. In the first place, corrosion didn't happen all over an esper body, it happened on their core, taking root like a disgusting black vein coiling up their soul. It was probably why he had such an effective guiding, because rather than taking a roundabout technique like visualization, he attacked the roots of the problem.
