These Mantras include, Mantras of the deities listed below:
1. Sharabheshwar - it the most dangerous Upasana in Sanatan Dharma even for Gods. The person who does Sharabheshwar Upasana cannot be harmed even by the Gods.
2. Batuk Bhairav
3. Mahakal Bhairav
4. Krodh Bhairav - This Upasana is also forbidden without initiation.
5. Martand Bhairav
6. Hanuman as one of the 51 Veers
7. 10 Mahavidya - Their Sadhana doesn't need Deeksha but their Sadhana cannot be completed without the guidance of a Guru otherwise there will be dangerous results.
12. Apsara, Kinnareshwari and Yakshini Sadhana.
13. Shudra Sadhana like Bhut Sadhana, Pishach and Pisachini Sadhana
14. Kaula Achar – this is very very secretive kind of path of Upasana as compared to Dakshin Achar and Vaam Achar. It combines both. This Upasana as well as Kaula Achar Sadhana are very very secretive and hideous even for great Tantrika and Rishis. Rarely does any one know about a Kaula Achar Sadhak.
Their Mantras also are very rare and almost impossible to find.
15. Kamakala Kali – The most auspicious but the most difficult to please of Kali. Only and only due to great good deeds does one get to do her upasana.
16. Shri Vidya Upasana – this includes Bala Tripur Sundari, Shodashi and Maha Tripur Sundari.
First, the Sadhak gains Siddhi over Bala Tripur Sundari and then goes to Shodashi and finally Maha Tripur Sundari. She is also called as Lalita.
17. Pratyangira and Vipreet Pratyangira
All those above God's worship or Sadhana cannot be begun without Deeksha.
Other than the Mantra Sadhana procedure, I have shared, sometimes the Mantra Sadhanas have their own requirements like Kshetrapal Puja, Dvarpaal Puja, Yogini Puja, Bhairav Puja, Nav Grah Puja, etc.
All of these have not been shared by in the procedure because they do not apply to every Sadhana. One must hence get the said knowledge from a Guru
If the Sadhak doesn't have the Idol or Yantra of his god, he can do the Japa in a Shivalay or he can also do Japa by facing - Sun, River, Vishnu, Pure Ghee Diya, a Havan, cow, or his Guru.
Keep in mind that there is difference between unavailability and unwillingness to do something. God knows well whether you actually had problem in buying the required articles or you were ignoring it. No one can fool god.