Before we proceed to eighth āvaraṇa, we should know about tithi nityā devī-s as they are worshipped in the outer side of the innermost triangle. Before entering into eighth āvaraṇa we will be worshiping Her four weaponries placed outside the innermost triangle. This will be discussed in the next part.

Tithi nityā devī-s represent fifteen digits of the moon and each digit is known as tithi or lunar day. There are fifteen tithi-s or lunar days and each tithi is represented by a nityā devī and hence they are known as tithi nityā devī-s. Technically speaking, there are only fourteen tithi-s and the fifteenth tithi is either full moon (pūrṇimā) or new moon (amāvāsyā). Fifteenth lunar day, either full moon (pūrṇimā) or new moon (amāvāsyā) is represented by Mahākāmeśvarī Herself.  Pañcadaśī has fifteen letters and each of these letters represent one kalā (digit) of the moon. But, kalā also means sixteenth part (1/16). But we have only fifteen letters in Pañcadaśī mantra. The sixteenth kalā is Ṣoḍaśī bīja śrīṁ(श्रीं), which is hidden and always remains subtle. As there are only fifteen tithi nityā devī-s, how to worship the sixteenth Ṣoḍaśī kalā? Answer to this question is considered as secret, as the answer reveals Mahākāmeśvarī. Sixteenth kalā is worshiped in the bindu, the place of Śiva. But in the bindu, Śiva is not worshiped while worshipping tithi nityā devī-s, but Mahākāmeśvarī is worshiped. This also subtly conveys the union of Śiva and Śakti. Though there is no separate procedure for Ṣoḍaśī upāsaka-s (those who are initiated into Ṣoḍaśī), when Mahākāmeśvarī is worshipped in the central bindu, the above aspect is to be contemplated. It would be ideal to worship Mahānityā (Mahākāmeśvarī) in the bindu with Ṣoḍaśī mantra for the sixteenth kalā, though it is not explicitly mentioned; but it is implied. Texts say that while worshipping Mahānityā, Pañcadaśī mantra should be encased (sampuṭīkaraṇa) between two aḥ (अः). Each nityā devī represents fifteen vowels from a to aḥ (अ to अः). But, those who are initiated into Ṣoḍaśī should use Ṣoḍaśī mantra, instead of Pañcadaśī mantra.

It is also said that during śuklapakṣa (waxing moon), tithi nityā devī-s should be worshiped from 1 to 16 (anticlockwise) as shown in the image. But during kṛṣṇapakṣa (waning moon), they should be worshiped in clock wise manner, i.e. from 16 to 1. However, one has to follow what his or her Guru says. In Śrī Vidyā worship, one has to meticulously follow what his or Guru says and there should be no deviation from his instructions, as he follows the traditions of his Guru and Paramaguru. But, it should always be remembered that he should be a Guru, who has attained mastery over the various types of worshiping Śri Cakra and should remain with Parāśakti all the time. Each tithi nityā devī have their own yantra-s and mantra-s. They have their own mūlamantra-s, āvaraṇa pūjā-s, etc. The innermost triangle is formed by the first three tithi nityā devī-s, viz. Kāmeśvarī, Vajreśvari and Bhagamālinī, each representing one corner of the triangle. Though as tithi nityā devī-s, they do not hold the innermost triangle, they hold this triangle as three devi-s representing three guṇa-s. This will be discussed in the next āvaraṇa, viz. eighth āvaraṇa. In fact, the innermost triangle is held by them. However, there are other views on this, which says that Lalitāmbikā, Kāmeśvarī nityā and Bhagamālinī nityā hold the innermost triangle. But this argument cannot be accepted. When Lalitāmbikā is seated on the lap of Śiva, obviously, She cannot be holding this triangle. Further, She cannot be compared to other nityā devī-s, who function under Her.

Following are the tithi nityā devī-s and their abode is marked as 1 to 15 in the image above and mentioned in anticlockwise manner.

Worship of tithi nityā devī-s begin with the worship of Mahānityā, Lalitāmbikā. She is worshipped like this in the bindu, three times using the following mantra.

Om aiṁ hrīṁ śrīṁ (ॐ ऐं ह्रीं श्रीं) followed by the initiated mūlamantra (either Pañcadaśī or Ṣoḍaśī) and at the end of mūlamantra alphabet aḥ (अः) is recited followed by Lalitā Mahātripurasundarī Parā Bhṭṭārikā pūjayāmi (tarpayāmi) namaḥ. Tarpayāmi is included only while performing navāvaraṇa pūjā. Navāvaraṇa pūjā will be dealt with separately, in due course. 

1. Kāmeśvarinityā कामेश्वरिनित्या (nityā is to be suffixed to all the names);

2. Bhagamālini भगमालिनि; 3. Nityaklinnā नित्यक्लिन्ना;

4. Bherunḍā भेरुन्डा; 5. Vahnivāsini वह्निवासिनि; 6. Mahāvajreśvarī महावज्रेश्वरी;

7. Śivadūtī शिवदूती; 8. Tvaritā त्वरिता; 9. Kulasundarī कुलसुन्दरी;

10. Nityā नित्या; 11. Nīlapatākā नीलपताका; 12. Vijayā विजया; 13. Sarvamaṅgalā सर्वमङ्गला;

14. jvālāmālinī  ज्वालामालिनी; 15. Citrā चित्रा;

Finally Mahātripurasundarī Parā Bhṭṭārikā preceded by initiated mūlamantra in the bindu. She is known as Mahānityā. 

Fifteenth tithi is either full moon or new moon and hence She is worshiped on these days. It is also said that on full moon day, She is in the form of Pañcadaśī mantra and on the new moon day, She is in the form of Ṣoḍaśī mantra. There is a reason for this, which is also considered as highly secretive. During new moon day, both sun and moon come together signifying the union of Śiva and Śakti, which is explained in Lalitā Sahasranāma 999 Śiva-śakty-aikya-rūpiṇī. Based on this principle, it is said that Ṣoḍaśī surely gives liberation. Though, She is the cause for liberation, merger of the individual soul with the Self happens only with Śiva. For the same reason, She is addressed as is Śiva jñāna pradāyinī in Lalitā Sahasranāma 727. Merger with Śiva can happen only if She is fully realized. That is why, the knower, the path of knowing and the known should become one during contemplation. Liberation is possible only if She fully pervades our mind. Unless we become one withParāśakti, obviously, when She unites with Śiva, merger of our individual soul cannot merge with Śiva. Sixteenth kalā is invisible and immortal. There is a reference to this in Bṛhadāraṇyaka Upaniṣad (I.v.14). The Upaniṣad says, “Nights and days are his (Hiraṇyagarbha*) fifteen digits and the constant one is His sixteenth digit. …..Through this sixteenth digit, he permeates all these living beings on the new moon night….” It is also important to note that Śiva too has sixteen kalā-s and it is said that Śiva’s lunar and solar aspects culminate.

This is the reason, why Ṣoḍaśī is considered as the most powerful mantra and should not be initiated to those who are not worthy of it. A Guru takes extraordinary care before initiating someone intoṢoḍaśī. Literally, Guru is paving way for the liberation of his disciple when he initiates him or her intoṢoḍaśī. It is often believed that a Guru does not initiate a person into Ṣoḍaśī without Her approval.

Many of these tithi nityā devī-s are referred in Lalitā Sahasranāma.

* Hiraṇyagarbha: Vedānta Paribhāsā a 17^th century scripture explains hiraṇyagarbha. It says “Hiraṇyagarbha is the first soul to be born and is different from Brahmā, Viṣṇu and Śiva.”  The subtle body consisting of the five vital forces, the mind, the intellect and the ten organs is produced from the five basic elements.  This paves the way for the soul to experience the result of actions or in other words it causes karma-s. The subtle body is of two kinds, superior and inferior.  The superior one is the subtle body of hiraṇyagarbha and the inferior is the subtle body of living beings.  The subtle body of hiraṇyagarbha is called as mahat or the cosmic intellect and the subtle body of living beings is called ego.