Board Thread:General Discussion/@comment-66.27.75.229-20150621173950/@comment-66.27.75.229-20150621180336

http://storyofevil.wikia.com/wiki/Elluka_Clockworker

In this one, it states that Elluka killed Irina and gained immortality because of it.

I'm fairly new to this series, so I'm not sure which version would be considered more canonical.