Over ten years ago, I participated in a Multi-Cultural Interdisciplinary Unit project; my group researched Russia. In the course of our studies, we discovered the Best Holiday Ever: Igbi.
To the best of my knowledge, the Internet contains only a handful of pages with information on Igbi. There is my Igbi page, a mention on familes.com, an article in Wilson's Almanac, and this Russian museum's page. The other pages I have seen are in Russian.