The following mantra is to pacify harm from naga possession and also to purify negative karma and sicknesses such as heart disease, leprosy, cancer and so forth. This is explained in the tantra from The Compassionate Eye Looking Buddha, Lotus Net.  This is the mantra “Exalted Chenrezig Lion's Roar,” (Skt: Arya Avalokiteshvara Simhanada): 

OM AH HRIH SIMHANADA HUM PHAT

Buddha’s name mantra:

CHOM DEN DE DE ZHIN SHEG PA DRA CHOM PA YANG DAG PAR DZOG PAI SANG GYE OZER CEA GYEN GYAL PO DRI MA ME PA DA WAI DRON MA LA CHAG TSAL LO (21x)

Buddha's name mantra also protects from paralysis and from lightning.

Other mantras:

OM TONBOLLI TONBOLLI PHIG TÜM MI SHIG SÖ SVAHA (7X)

OM TONBOLLI TONBOLLI SUR SUR ME ME SHIG SHIG SVAHA (7X)

OM SHRI MATI ASUR SVAHA (7X)

SAKATA RUDA AMAYA TETU NATAY SHANA LAYA SOHA (7X) [Note: this mantra is unchecked.]

Reciting the above mantras 21 times daily, or at least seven times daily, protects one against pollution caused by spirit possession (paralysis). This is stated by Dromtompa, who was Lama Atisha’s translator, Originator of the Victorious Ones and Embodiment of the Compassionate Buddha.

If you are already suffering from paralysis, recite these mantras seven times each day to prevent having a second or third paralysis, which makes recovery difficult. Also, if you recite these mantras many times each day, you will not receive harm from upper spirits, as is mentioned in Gyalwa Ensapa’s collection of teachings.

Note: Gyalwa Ensapa was a disciple of Lama Tsongkhapa’s and, like Milarepa, became enlightened in one brief lifetime.