Quoting from: https://www.plug.game/kingsraid/1030449#/

Briefly stating: https://youtu.be/4FB9JgTdOPQ Summary: This is a bug said to have been discovered from last June but remains unfixed until 30/03/2019. To prove the existence of this bug, I am uploading this video on Youtube. In this video, a technique that obtains single time summon FOR FREE has been revealed. This technique takes advantage of a bug in the game, which has been fixed under the table without any apology or compensation. This is an infringement to player right of enjoying a fair game environment, and Vespa should not be freed from an official apology to all the players. Besides, necessary measures must be taken and players' not taking advantage of the bug must get their fair share of compensation. To read full context please go to the original site. Thank you.