For 10 points, name this smaller of the two major branches of Islam, along with Sunni.
One doctrine held by this religious group is "occultation", which claims that the Mahdi was born but disappeared from human contact. Sects within this group include the more mystical Ismailis, and the majority Twelvers. These adherents believe in a series of divinely appointed imams and reject the caliphs in favor of Muhammad's (*) cousin Ali. This group is currently most prominent in Iraq and Iran. For 10 points, name this smaller of the two major branches of Islam, along with Sunni.
One doctrine held by this religious group is "occultation", which claims that the Mahdi was born but disappeared from human contact.
{Shi'a} Islam [or {Shi'ite}; prompt on {Islam}; accept {Twelvers} before "{Ismailis}"]