Did you know that the first quest for the dark brotherhood 'a knife in the dark' is a contract by Claudius Arcadia who is in the imperial prison for conducting the black sacrament.
![[Image: 600px-OB-npc-Claudius_Arcadia.jpg]](http://images.uesp.net/thumb/2/29/OB-npc-Claudius_Arcadia.jpg/600px-OB-npc-Claudius_Arcadia.jpg)
You can find this out by reading Claudius's journal, the last entry within his journal states 'Entry 3: It worked! Last night I was visited by someone, a representative from the Dark Brotherhood! The Night Mother heard my prayers! The money was exchanged, and the man promised me I would have satisfaction. I don't know where he's hiding, and neither does the Dark Brotherhood, but as soon as he's located, Rufio will die!'
![[Image: 300px-Rufios_Mug.jpg]](http://images3.wikia.nocookie.net/__cb20110709152623/elderscrolls/images/b/b6/300px-Rufios_Mug.jpg)
the reason isnt stated with in the journal however when talking to Rufio If you accuse him of having done something to deserve death, Rufio makes the following comment: "No! Please! I didn't mean to do it, you understand me? She struggled! I... I told her to just stay still, but she wouldn't listen! I had no choice!" giving a hint that he harmed ( or worse ) Claudius's daughter or wive!
Sources:
http://www.uesp.net/wiki/Oblivion:Claudius_Arcadia, http://www.uesp.net/wiki/Oblivion:Claudius_Arcadia, http://www.uesp.net/wiki/Oblivion:Rufio