Well, I'm no master on Islam, but I decided to tackle this node simply because it was empty, and because it accidentally reminded me of Final Fantasy.
Apparently (at least this is what I could gather), Ashura is the name of a battle that took place in Iraq on the Euphrates River on October 20, 680 AD. It wasn't really much of a battle, but more of a massacre. A large army sent by the Umayyad regime cornered a group of about one hundred people, and then brutally killed them all.
The reason that this battle seems to be important is because of Husain, grandson of Muhammad, the leader of the people who were killed. Even in the face of certain death, he stood up for Islam and became a martyr. Ashura is commemorated on the 10th of Muharram every year to remind the Islamic people of the sacrifices of the family of the Prophet.