From the publisher's website:
Greetings and welcome to the world of Diamonsters! From the designer and artist of the best-selling Machi Koro card game, Diamonsters is a fast-paced monster collecting card game! In Diamonsters, each player begins with the same hand, and the first player to collect three monsters of the same type or five diamonds wins. But it’s not so simple, some monsters are more valuable than others, and some will eat the diamonds you fought so hard for!