All deities can help. Not a big deal. However Shiva and Dhanavantari are associated with healing. Among the Aryans, Rudra was the healer, who later merged into Shiva. Lord Dhanavantari emerged out of the milk-ocean during its churning by Gods and demons. Dhanavantari Day is celebrated two days before Diwali.
Mantras, many; but the most popular is:
Trayambakam yaj
āmahe, sugandhim pushti-vardhanam l
urv
ārukam iva bandhan
ān, mrityor-mukshiya m
ā-amrt
āt ll
1. We Worship the Tryambaka (the Three-Eyed One),
2: Who is Fragrant (as the Spiritual Essence), Increasing the Nourishment (of our Spiritual Core) l
3: From these many Bondages (of Samsara) similar to Cucumbers (tied to their Creepers),
4: May I be Liberted from Death (Attachment to Perishable Things), So that I am not separated from the perception of Immortality (Immortal Essence pervading everywhere).
Mahamrityunjaya Mantra - Wikipedia
This is known as Maha-mrityun-jaya mantra. The 'great victory-over-death mantra'. The story goes that Rishi Mrikandu and his wife Marudmati did not have any children. So, they started praying to Lord Shiva. After a long penance they finally managed to make Lord Shiva happy. Lord Shiva finally appeared before them and agreed on giving them a boon of a son. However, Lord Shiva gave them a condition. The son will either be very intelligent but have a short lifespan or, the son will have a long lifespan but will not be very intelligent.
Rishi Mrikandu and his wife decided to go for the first option and Lord Shiva blessed them with a son who was named as Markandeya. However, Lord Shiva said that the child will live only for 16 years. Markandeya was never aware of the truth of his birth and the future that awaited him. He was however a staunch devotee of Lord Shiva. Gradually as Markandeya started approaching the age of 16, his father and mother became worried. He then insisted on knowing the reason and finally his parents revealed the truth and the future which was not far.
After knowing the whole thing, Markandeya started penance sitting in front of Shiva Linga. When he turned 16, he was still in deep meditation and prayer. That is when Lord Yama or Yamaraj sent a messenger to take Markandeya. However, Markandeya was so deeply lost in prayers that the messenger had to return back. As a result of this, Lord Yama himself came to take Markandeya. Markandeya didn’t want to go and embraced the Shiva Linga and surrendered himself to the mercy of Lord Shiva.
Lord Yama, in order to complete his duty decided to apply force and threw his noose on Markandeya. Unfortunately, the noose fell around Shiva Linga. This made Lord Shiva angry and he appeared in front of Markandeya and Lord Yama. Lord Shiva was so furious that he instantly killed Lord Yama. That is when other gods came to Lord Shiva and stated that death of Lord Yama will completely disrupt the universe’s balance and hence, reviving Lord Yama was necessary.
Lord Shiva agreed to the plea of other gods but put forward a condition that the boy Markandeya will live forever. Everyone agreed to the condition and Lord Yama was revived by Lord Shiva. So Sage Markandeya is one of the seven immortals in Hinduism. Because Lord Shiva killed Lord Yama, Lord Shiva is also known as Kalantaka or Ender or Destroyer of Death. Lord Yama is considered as Death in Sanatana Dharma which is known to the world as Hinduism. It is said that during his prayers to Lord Shiva, Markandeya created the Mahamrityunjaya mantra and that the mantra was known only to him.
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30 Interesting Mahamrityunjaya Mantra Facts
Shiva saving Markandeya from Yama (painting by Raja Ravi Verma).
Raja Ravi Varma was closely related to the royal family of Travancore of present-day Kerala state in India. Later in his life, two of his granddaughters were adopted into that royal family, and their descendants comprise the totality of the present royal family of Travancore, including the latest three Maharajas (Balarama Varma III, Marthanda Varma III and Rama Varma VII).
Raja Ravi Varma - Wikipedia