Please follow my advice and do not add billions of gems to your account the devs are watching the leaderbords and they are checking the accounts , please go only negative -9000 or less, if you go -9000 you will get around 2Milions gems , spend them all , dont hold anything ,thats safer in my opinion in case that you end up on first place in leaderbords and your account will be checked by the devs. this hack works only on events that you have to spend gems, the game have automated anticheat , but seems that is not working.
https://play.google.com/store/apps/details?id=com.abi.legendofsurvivors&pcampaignid=web_share