Nicodemus Archleone carries a noose at his neck, which gives him access to certain kinds of magic.
Believed to be the noose Judas
used to hang himself, it is a powerful magic object, capable of death and entropy curses. [Footnote 1] The noose does not get soaked in blood. 
In the series Edit
Death Masks Edit
Main article: Death Masks
Death Masks, the noose allows Nicodemus Archleone to cast a Barabbus curse against Harry Dresden.
Small Favor Edit
Main article: Small Favor
Small Favor, the noose protects Nicodemus Archleone from any harm except from the noose's itself. Archleone has worn it for centuries, a weakness which allows Harry Dresden to put Archleone in a corner.
Skin Game Edit
Skin Game, in an attempt of saving Harry Dresden from the attention of the Genoskwa, Karrin Murphy threatens to remove Archleone's noose from him and hand it to the Church. However, she fails.
Judas Iscariot - wikipedia