There's such system in KRO already, called Lapine Dukdak box.
There are 5 type of Dukdak box ( can be obtained randomly from Lapine Dukdak Box)
1. Kitcoin Costume Dukdak box : consume 1 costume obtained from kitcoin to gain new 1 costume that obtained from kitcoin too.
2. Pet Egg Dukdak box : consume 2 different kind of pet egg to gain 1 Taming Gift Set. Cannot use Novice Poring Egg as ingredient.
3. Collectiom Dukdak box : consume 10 ea of 10 different kind of loots to gain new ones. items that are sold by NPC cannot be used.
4. Costume Enchant Stone Dukdak box : consume 3 different kind of costume enchant stone to gain new 1 costume enchant stone.
5. Shadow Dukdak box : consume 3 different kind of shadow gears to gain new 1 shadow gear.
That's the way to gain limited costumes, enchant stones and shadow set which sold in the past.
http://ro.gnjoy.com/...q=184&curpage=1
Edited by Sigma1, 20 October 2016 - 06:45 PM.