OS X El Capitan won't work and is not recognized on UniBeast
The officially supported way to create a USB OS X Installer, for OS X Mavericks and later, is to use createinstallmedia from within the downloaded installer application bundle.

Have a look at: Create a bootable installer for OS X

The following is from the link above:


  Use the 'createinstallmedia' command in Terminal
  
  
  Download the OS X installer from the Mac App Store. Quit the installer if it opens automatically after downloading. The installer
  will be in your Applications folder.
  Mount your USB flash drive or other volume. You could also use a secondary internal partition.
  Open the Terminal app, which is in the Utilities folder of your Applications folder.
  Use the createinstallmedia command in Terminal to create the bootable installer. Examples of this command are in the next section.
  For detailed usage instructions, make sure that the appropriate
  Install OS X app is in your Applications folder, then enter one of the
  following paths in Terminal:
  
  
  Path for El Capitan:

/Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia

  
  Examples
  
  This is the basic syntax of the command. Replace volumepath with
  the path to your USB flash drive or other volume, and replace
  installerpath with the path to the Install OS X app. 

createinstallmedia --volume volumepath --applicationpath installerpath

  
  The following examples assume that the OS X installer is in your
  Applications folder and the name of your USB flash drive or other
  volume is MyVolume:
  
  Example for El Capitan:

sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app



Note: You can substitute Mavericks or Yosemite for El\ Capitan in the above command examples.