Now first and foremost (and as usual) there is no information as to what this is, so it's (yet again) a case of work it out for yourselves.
So looking at it there's no clear path to progress through the 10 stages, there is an option to 'unlock' premium for £5.79 (surprise), and 2 options (the XP & skull at the top) both 'seem' to offer a 24 hour reward for a mere 12,000 rubies for one and 1,800 for the other


Even if you have a full clan of 20 that's 6,900 rubies each for some pretty shoddy rentals, exception being the 11* SM which withstands godlike boost, but again if it's a rental it would be one expensive SM to do all the upgrades within the 24 hours to make it much use.
Images below for reference, reference of GameLofts continuing greed.