According to the Dawoodi Bohra Faith, in time of the Imam’s seclusion, Dawat al-Haqq is promulgated and administered by three spiritual ranks (hudood): the Dai al-Mutlaq and under his auspices the Mazoon al-Mutlaq and then the Mukasir.
This system of Dawat has been elaborated on by the notable Fatimid scholar Syedna Ja’far b. Mansur al-Yaman on the authority of the Fatimid Imam al-Mu’izz SA:
When the Imam goes into concealment, his Dawat remains existent—even if only in a single section of the earth—by his command, or by command of his predecessor who appointed him and signaled his imamate. The Imam is present through the presence of his hudood, who indicate his presence, conduct his Dawat, calling the people to his walayat. They carry out the rites of his Dawat, its farizats and its nawafil, explicating what is lawful in it and what is unlawful.
The Imam’s Dawat is present through the presence of three rank-holders: Dai-l-mutlaq (Dai with full authority), Mazoon mutlaq (Mazoon with full authority), and Mazoon Mahsoor (Mazoon with limited authority, also known as the Mukasir, or Breaker of False Arguments)... Therefore, the Imam, peace upon him, is said to be present through the presence of these hudood. It is known that God Most High could not be comprehended by any one of His creatures, that no one could speak with him, with good or bad, benefit or harm, were it not for the presence of the Prophet, Wasi, and Imam to guide and direct them; God, may He be praised, is manifest and present through those hudood [Prophet, Wasi, and Imam]. In the same manner, the Imam, peace upon him, is manifest and present through these hudood [Dai, Mazoon, and Mukasir]. The Imam’s knowledge and aid flows to them continuously, and his barakaat encompasses them always. Indeed, they are aided by the incessant and uninterrupted flow of the light of God.
(Translation of text by Syedna Ja’far b. Mansur al-Yaman qtd. In Syedna Taher Saifuddin’s Risalat Daw’u Nooril Haqqil Mubeen. Click here for Arabic pdf of text link to PDF)