There are multiple artists with this name:
1) Age of Agony is a death metal band from Hungary. They were previously named as Silent Agony. They formed in 2002 releasing several demos called "Promo 2002" in 2002 and "The Dark Conquers All" in 2003 before releasing their debut album in 2005 called "War, Hate, Blasphemy" via Kárpátia Productions.
This lead them to make a split with Slugathor in 2006.
They came back from touring in 2008 and went into the studio to record "Follow The Way Of Hate" via
No Colours Records.
After some years, they released their follow up album to their 2008 album known as "Machinery of Hatred" in 2011 via Terranis Productions. Soon after they released a compilation via Sigillvm Tenebrae Records and Werewolf Promotions which consisted of their 2008 and 2011 albums along with their split with Slugathor, this was limited to 300 copies and sold as a Tape.
2) Age of Agony was a speed thrash metal band from Netherlands. They formed in 1990. They released two demos called "Fragments", in 1994, and "Threat of Things to Come" in 1998. However, they split soon after becuase of not being able to find an appropriate label to release their debut album.