[CentOS] alien?

Anyone know what repository alien's in? A yum list doesn't find it in
CentOS-Base.repo
CentOS-CR.repo
CentOS-Debuginfo.repo
CentOS-Media.repo
CentOS-Vault.repo
epel-testing.repo
epel.repo
rpmfusion-free-updates-testing.repo
rpmfusion-free-updates.repo
rpmfusion-nonfree-updates-testing.repo
rpmfusion-nonfree-updates.repo

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