Yes, most Area bosses drop a Monster Card which gives an item & meso drop rate buff for the specific area. The +% increase depends on the type of mob and actually isn't shown in the buff information, but we plan to fix this for the next patch. The rate buff for the Deo card is only +10%, but I've still found this to be useful for collecting cards. The rate goes up to +60% for area bosses like Lilynouch, Lyka, Dodo and Leviathan.
