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> that scarlet entity
It's likely how she showed herself so it's not certain that she looks that way, I think Snail used that name. It's the deity who created the Strengthening Divine Powers exercise in Falun Dafa. It was said in the book that Li merely passed it on from his masters.
After further interactions Scarlet showed things implying it was her possessing Li all along and that she made all exercises to create the movement and spread Qi Gong. That means she is a "futi" and the lecture about this turns back at the person who said it. This is part of the "disclaimer" in the text. Apply it back at itself and you see things no one wanted to admit.