Riaz Khan/AP
Abdul Rahim Muslim Dost, who is in his 50s, swore allegiance to the extremist group's leader Abu Bakr Al Baghdadi on July 1, just two days after Al Baghdadi declared the territory stormed by ISIS this year a caliphate.
Dost's positioning in Pakistan is another sign of ISIS' global ambitions, alongside the group's capture of a Libyan city on the Mediterranean coast.
His experience is suitably
He was also among the radicals who besieged the Grand Mosque in Mecca, one of Islam's holiest sites, in 1979. He escaped to Peshawar, Pakistan, where he was detained in late 2001 before being transferred to Guantanamo.
From there he would be transferred back to Afghanistan in April 2005 and released due to health problems. A leaked memo by Joint Task Force Guantanamo concluded that "the detainee poses a low risk, due to his medical condition [...] JTF GTMO recommends this detainee be released or transferred to the control of another country for continued detention."
Dost is also an author, who in 2006 published "The Broken Shackles of Guantanamo," the story of his time in the controversial prison.
Mohammad Zubair/AP
According to Dawn, an English-language newspaper in Pakistan, Dost's work involves creating and distributing propaganda in the form of pamphlets declaring that ISIS will expand to Pakistan, Iran, Afghanistan and beyond.
But in Pakistan especially, ISIS is antagonized by the Taliban and Al Qaeda, which publicly disavowed ISIS in February after a spat over its outsized ambitions.
Still, the group has attracted many would-be jihadists from across the world, and might have a similar pull on some of the Taliban's ranks.