Board Thread:Questions and Answers/@comment-64.89.248.90-20130318031036/@comment-885547-20130318114418

to get pure dragon, both side is must filled with legend type dragon or specific list (since 4 slot is filled by legend dragon type).

the problem is if rate value is not enough to unlock all slot, so you can't get rare one. but you still can get pure elemental from this combination. but elemental dragon will filled 30 % if your rate value is 1000.