Maha Mantra– mantra for kali yuga.

Source : https://vedabase.io/en/

The Brahma Vaivarta Purana (related to Rathantara kalpa) mentions a ten thousand-year period, starting from the traditional dating of the Kali Yuga epoch, during which bhakti yogis (devotees in all traditions) will be present.^[33] Krishna foretold that Kali Yuga will be full of extreme hardships for people with ideals and values.

The Brahma-vaivarta Purana has words spoken by Krishna to Mother Ganga just before the beginning of the Kali Yuga (the age of quarrel and strife). The Kali Yuga began approximately five thousand years ago; that golden age is being described below by Krishna. Predicted in Brahma-vaivarta Purana 4.129, the fourth part of the Brahma-vaivarta is called Kṛṣṇa-janma-khanda. Chapter 129 is called Golokarohanam, because it describes how Krishna returns to His abode. This specific dialogue is between Krishna and Mother Ganga. Verse 49 is a question by Ganga, verses 50–60 are Krishna's answer.

This text is taken from the Brahma-vaivarta Purana [14] Text 59:

kaler daṣa-sahasrāṇi
madbhaktāḥ santi bhūtale
ekavarṇā bhaviṣyanti
madbhakteṣu gateṣu ca

For 10,000 years of Kali such devotees of Mine will be present on earth. After the departure of My devotees there will be only one varna.

The above is supported in 4.90.32–33:

kalau daṣa-sahasrāṇi
haris tiṣṭhati medinī
devānām pratimā pūjyā
śāstrāni ca purāṇakam

(Sri Krisna said:) Lord Hari will stay on this earth for the first ten-thousand years of Kali-yuga. Till then gods will be worshipped and the Puranas and scriptures will also be present.

Source : https://en.wikipedia.org/wiki/Kali_Yuga