When Ren engaged the three-way beast fusion, his consciousness violently expanded outward. His sensory network artificially bloated to an almost god-like scale compared to any other tamer.
And during those secret subterranean practice sessions he did in Selphira's chamber full of concealing artifacts, swimming in that expanded state of perception, it hadn't cost him a single ounce of effort to detect her beasts' movements.
He had felt the distant, faint outlines of her heavy presences shifting in the dark. He had watched the invisible circular formation quietly rearranging itself, day after day, hovering just on the razor's edge of what even a Tamer of his caliber should theoretically be able to sense without the mushroom being active.
Selthia had confidently parked her apocalyptic strike force right on that boundary line, completely convinced she was invisible.
To the baseline, everyday Ren, she would have been.
