For the なぞなぞオーダー (Riddle Order) event from 21 - 28 July 2016, you need to kill a certain amount of enemies based on the clues given on the website, to obtain a good number of rewards.

とらとりゅうのあいだは？ (Kill 10 x Rabbits) とびらのかげにいるおとこ (Kill 5 x Saurians)

ＹＹＹＹＹＹＹＹＹＹ (Kill 3 x Wights)

なぞなぞといえば？ (Kill 2 x Sphinxes)

You will receive a notification once you’ve succeeded killing the correct targets, as shown above.

Rewards (corresponds to above riddles):