Thread:Silverisimo/@comment-24250059-20131221224336/@comment-24263188-20140502173911

^ BB = Boosted breeding. It's supposed to increase your chances of breeding Rare, Super Rare and Ultra Rare dragons.

When choosing two dragons for the den, the usual breed button costs 200 coins, this option is the button above that. It usually costs 12 gold and doesn't work, but surprisingly works during free events like these.. expires anytime today, I reckon you might still have a shot at it :)