dungeons and dragons – Where can I find lore about the Ichor Lance?

This particular artifact has caught my attention. I can barely find any lore pertaining to it. It has a blurb about how it was used by Zagig and Iggwilv to imprison Fraz-Urb’luu in Greyhawk but that’s the only thing about it I can find.
Is there anything else I missed, or, is this just a Maccguffin or a Deus ex Machina?