Answer

If by “Navkar C” you mean Navkarshi or taking a Navkar Mantra vow/jap, the main mantra is the sacred Navkar Mantra itself.

There is no separate “special mantra” required beyond the Navkar Mantra.

Navkar Mantra

णमो अरिहंताणं णमो सिद्धाणं णमो आयरियाणं णमो उवज्झायाणं णमो लोए सव्व साहूणं

एसो पंच णमोक्कारो सव्व पावप्पणासणो मंगलाणं च सव्वेसिं पढमं हवई मंगलं

How to Take / Do Navkar

You may do it respectfully like this:

• Sit in a clean and peaceful place.
• Calm your mind and body.
• Fold your hands or sit in meditation posture.
• Recite the Navkar Mantra with faith and awareness.
• You can chant it 9, 27, 54, or 108 times according to your capacity.
• Focus on bowing to the five supreme beings: Arihant, Siddha, Acharya, Upadhyay, and all Sadhus.

Spiritual Understanding

Navkar Mantra is not a prayer for worldly favors. It is a prayer of reverence to the highest spiritual qualities. By chanting it, we remember purity, liberation, discipline, knowledge, and saintliness.

Takeaway

There is no separate special mantra needed. Chant the Navkar Mantra with purity, respect, and concentration.