Arisaema Rhizome Classic Formulas … Natural Herb Library

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Dries dampness and transforms cold-damp or stubborn phlegm - Tian Nan Xing is warmer, drier, and more forceful than Ban Xia when thick obstructive phlegm needs to be broken up.
Dispels wind-phlegm and opens the channels - classic use includes facial paralysis, numbness, dizziness, and stroke-like channel obstruction when phlegm blocks the collaterals.
Stops spasms and addresses phlegm-obstructed seizures - it is used when turbid phlegm closes the clear orifices and contributes to epilepsy or convulsive disorders.
Dissipates swelling externally - topical application extends to abscesses, painful nodules, and other toxic swellings.

Dao Tan Tang - classical stubborn-phlegm formula in which Tian Nan Xing helps dry dampness and break up obstructive phlegm.
Qing Zhou Bai Wan Zi - famous wind-phlegm channel-obstruction formula using Tian Nan Xing for numbness, facial deviation, and stubborn phlegm in the collaterals.
Wu Xian Wan - classical seizure formula in which Tian Nan Xing helps address phlegm closing the clear orifices.

TCM Wiki lists Tian Nan Xing as bitter, acrid, warm, and toxic, entering the Lung, Liver, and Spleen with core actions of drying dampness, resolving phlegm, extinguishing wind, and reducing swelling.
Classical comparison texts say Ban Xia primarily works the Stomach and intestines, while Nan Xing more strongly travels the channels and collaterals for wind-phlegm.
Standard modern processing with ginger juice and alum reflects the long-standing recognition that the internal medicinal is safer and clinically more usable after preparation.