Mahdi Army fighters loyal to Shiite cleric Moqtada al-Sadr march in the Iraqi city of Najaf on Saturday. Sadr has been publicly calling for a Shiite fighters to form "Peace Brigades" and protect Islamic shrines and holy sites. (Ahmad Mousa/Reuters)

As Iraq's turmoil continues, a controversial figure has reportedly returned to Baghdad. The Times of London reported this week that Abu Deraa has been spotted in the Iraqi capital, with al-Arabiya pointing toward a video posted to YouTube by Shiite militants that appears to show the notorious Shiite militia leader welcomed home after years of exile.

Abu Deraa's return to Baghdad is a worrying sign of how the sectarian rift in Iraq keeps growing, with Shiite militias gaining traction in Baghdad after Sunni Islamists under the banner ofthe  Islamic State of Iraq and Syria (ISIS) took over much of the rest of the country. Many old faces are reappearing, and the apparent reemergence of Abu Deraa is another reminder of just how many loose ends went untied after the 2003 Iraq invasion and the sectarian violence that followed.

Born Ismail al-Zerjawi, it was under his pseudonym that Abu Deraa (which means "Father of the Shield") became well known almost a decade ago. In 2006, Abu Deraa was described by The Post as "Iraq's most notorious death squad leader." A profile from the Jamestown Foundation that same year says that Abu Deraa and his Shiite militant followers were suspected of unusual cruelty when killing their Sunni victims: torturing them before offering them their choice of gruesome murder method, before leaving their bodies in the al-Seddah sector of Baghdad's Sadr City district (an area that became nicknamed the "Happiness Hotel.") There had been reports that Abu Deraa had died a few years ago, but it appears that he had been living in exile, possibly in Iran.

Worryingly, Abu Deraa isn't the only familiar face apparently making a return. Izzat Ibrahim Douri was a high-ranking leader in the Iraqi army before the 2003 invasion and a key aide to Saddam Hussein, and he later became Iraq's most wanted man, known as the "King of Clubs" because of his position in the deck of cards given to U.S. troops during the invasion. Douri, rumored to have died a few years back, is now suspected of leading Sunni Baathist loyalists who are working with ISIS. Britain's Daily Telegraph reports that Douri is now thought to lead other supporters of the old regime in the Naqshbandi Army and that its military importance may be equal to ISIS's in some areas.

Meanwhile, Moqtada al-Sadr, a Shiite religious leader with a fearsome reputation, is also retaking the center stage. Just months ago, Sadr had suggested he would be withdrawing from Iraqi politics, apparently out of disdain for Prime Minister Nouri al-Maliki. However, the onslaught of sectarian violence has led to a reemergence for Sadr, who returned to Iraq from a self-imposed exile in 2011. The cleric, known for his anti-American views, has publicly called for Shiite fighters to form "peace brigades" and protect Islamic shrines and holy sites. Many are worried that Sadr may be attempting to regroup the Mahdi Army, the Shiite militia well known for its links to brutal sectarian violence a few years ago.

These three men — some of the most notorious figures in the history of modern Iraq — may currently be overshadowed by the threat from ISIS. However, as their reputations suggest, their reemergence is not likely to be a good thing for Iraq.