Conversation so far:
what is Requiem for Indifferent and Retrospect in regard to Epica?
On December 1, the band announced that the name of the album would be Requiem for the Indifferent.
what songs were on that album?
CANNOTANSWER.
what year did the album come out?
The single was released through Nuclear Blast on 25 September 2012.
was is popular?
on March 23, 2013, they would celebrate the 10th anniversary of Epica in Eindhoven, Netherlands.

Question: how did they celebrate?
Self-contained rewrite: how did Epica celebrate?