Muhammad bin Ali, surnamed al-Mohtadi is reported to have born in 500/1106 in the fortress of Lamasar. He was the first Ismaili Nizari Imam to be born in Iran. He is also called Muhtab and Muhammad I.
The Seljuq sultan Sanjar was ruling in Iran, while Iraq was under the control of sultan Masud. Sultan Malikshah III (547-548/1152-1153) was followed by Sanjar, and then Muhammad II (548-555/1153-1160). In Baghdad, the Abbasid caliph Rashid (529-530/1135-1136) had been dethroned by sultan Masud, and Muktadi had been placed on the throne, who ruled till 555/1160. He was harsh against the Ismailis, and caused the manuscripts of "Ikhwan as-Safa" burnt in Baghdad, alongwith the writings of Ibn Sina in 545/1150. In Egypt, the Fatimid empire was in the hand of Abdul al-Hafiz (524-544/1130-1149), succeeded by al-Zafir (d. 549/1154) and al-Faiz (d. 555/1160).
Al-Mohtadi is said to have reorganized the Ismaili mission from his base in Lamasar. In 530/1136, he deputed dai Zayn bin Abi Faraj in Syria with a sealed letter. This letter is preserved in the manuscript of a dai Ibrahim bin Abi'l Fawaris, who copied it on 16th Shawal, 890/1502, in which al-Mohtadi addressed to his Syrian followers that:
"Verily, I am your Mawla Muhammad bin Ali bin Nizar. May God curse one who denies to believe the truth and covers it. We have charged dai Zayn ibn Abi Faraj ibn Abi'l Hasan ibn Ali with this pledge to make the truth cleared for you for the manifestation of the truth...."
In this letter, al-Mohtadi traces his lineage from al-Nizar for four times, and concludes that, "After the termination of the 40th time(dawr-i arb'in), and (then) also after passing away of the 70th period (mudatu's sab'in), the time will be approaching for the appearance of the manifest truth (haq-i mubin) that will cause all the matters to obliterate and the earth will be glorified with the light of faith. The truth with His word (i.e., Imam) shall manifest in near future in the hearts of the seekers of gnosis."
The above letter had been written as soon as al-Mohtadi assumed the Imamate in 530/1136, describing the passing away of 40 years of dawr-i satr (concealment period) from 490/1097. He also foretold the appearance of an Imam in his descent after completion of 70 years on the whole. It was a prediction most probably for the Great Resurrection (qiyamat-i qubra) celebrated by Imam Hasan II, the grandson of al-Mohtadi, in 559/1164.
Kiya Buzrug had laid a firm foundation of the Nizari state for an independent territorial rule, and also minted the Nizari coin. He died in 532/1138 after ruling for 14 years. Al-Mohtadi appointed his son Muhammad bin Kiya as the third hujjat and ruler.