It celebrates the end of the 40-day Ashura period honoring Hussein's martyrdom.

CNN: Pilgrims flood Karbala on final holy day

The martyrdom of Hussein carries a significance for Shia similar to Christ's crucifixion, according to GlobalSecurity.org, an international security group.

CNN: Pilgrims flood Karbala on final holy day

Brought before the Ottoman ruler with the connivance of hostile rabbis to answer charges of sedition, Sevi converted to Islam rather than face martyrdom, and accepted a sinecure as the Sultan's head gatekeeper.

ECONOMIST: Jewish mysticism