Most secret thing in the world

12 imams, appointed, then bada`, knew each one one after other, or were known in the time of prophet (sallalahu alaihi wa ala alihi wa sallam), last one gone into concealment due to fear, or any other reason. I don’t know what about you, but for me, it was always hard to believe in this fairy tale. I guess that it was due to purity of my fitrah.
But shia books say that to understand imamate is not easy

It was reported by Muhammad ibn al-Hasan as-Saffar in “Basair ad-Darajat” (p 48) from Abu Abdullah (alaihi salam), and also in “Sahifa Abrar” (2/200) by Mamiqani:

ان امرنا سر في سر وسر مستسر وسر لا يفيد الا سر وسر على سر وسر مقنع بسر
Verily, our command is a secret in a secret, and a concealed secret, and a secret that is only known as a secret, and a secret upon a secret and a secret veiled by a secret

And at page 49 of the Basair, again from imam:

ان امرنا هو الحق وحق الحق وهو الظاهر وباطن الباطن وهو السر وسر السر وسر المستسر وسر مقنع بالسر
Verily, our command (amr) is the truth and the truth of the truth; and it is the exoteric and the esoteric of the esoteric; and it is the secret, and the secret of the secret, and the secret of the concealed place, and the secret veiled by the secret

Secret in the secret on the secret between most  secrets things. It is so secret that last imam with his command wasn’t seen around for ages