User blog comment:B214/Volume 17 spoilers./@comment-117.217.186.212-20140224111716/@comment-1359322-20140225043850

It's a hidden feature implanted by the God from the Bible into the 2 Sacred Gears.

The Boosted Gear has one of Albion's hidden ability and the Divine Dividing has one of Ddraig's hidden ability.

The Dividing Gear is something Issei just created by pure luck. The Dividing Wyvern Fairy is something unlock by the mutual understanding of the Two Heavenly Dragon.