This is a Health Mantra which is dedicated to the Hindu mother Goddess Mahakali to get relief from pain. Amongst the numerous Hindu Mantras for pain relief this mantra is probably the most powerful.
The Siddhi [mastery] over this Mantra is acquired during the period of any Eclipse, Solar or Lunar by reciting this mantra 10,000 times.
Then after acquiring Siddhi to get pain relief you have to take some water in a small glass and recite this mantra 21 times. This will Abhimintrit [bind] the water in the glass with this mantra. Then you have to give that water to the person suffering from pain.
If it is you who are suffering you can drink the water yourself.
Kali kali mahakali nomostute han han daha daha shulam trishulen hum fatt swaha ll
कालि कालि महकालि नमोस्तुते हन हन दह दह शूलं त्रिशुलेन हुं फ़ट् स्वहा ll