Re-rolling an account is when a player restarts the game with the intention of getting a unit they want from the initial free Rare Summon (or two at the moment, as Gems are being given a way due to the maintenance).
One method of re-rolling your account is by doing a factory reset on your mobile phone. This isn't exactly an efficient method of re-rolling your account as it means reinstalling every app on your phone, with no guarantee of not having to do it straight again afterwards!
There is an easier way of re-rolling your account if you have a rooted device. For those of you that don't know what a rooted device is, it's a device that has root access to every single file on the phone, usually you are restricted to your storage area. Rooting your device can go wrong and brick your phone, so do it at your own risk. If you'd like information on how to root your phone, there's plenty of info over at the XDA Developers forum.
If you're phone is rooted, then follow the steps below to re-roll your in game account:
Go into Settings > Apps and tap Brave Frontier.
Tap 'Clear data'.
Download Titanium Backup from the Google Play Store.
Allow Titanium Backup Superuser permissions, press the Menu button, scroll down and tap 'Manage Android ID...'.
Choose 'Create new (random) Android ID.
The device will now reboot, click Brave Frontier and it'll begin downloading the updates again. You'll be prompted to log in using Facebook or create a Guest account. Choose create a Guest account and sync it to your Facebook once you've got the units you're after.
To get 10 metal Gods:
Go to Social and Special: ID=22832167 You will receive your first metal God ! Well done ;p
To have the other metal gods, your friends must do the same things with your player ID (Go to menu and player info to get yours)
If not enough friends, you can invite yourself by clearing data in app settings (Android) and changing your android ID with titanium backup, restart the and phone launch the game (it should be new account), go to social and Special to put your ID (good account), then restore your android ID with titanium backup, clear brave frontier data in android app settings and enjoy ! Repeat this operation to have your 10 metal gods