The icon for this round was red, and different to the others on-screen, so I thought this might have unlocked a new character or something special – but really it was just another level with more bad guys to kill.
One of the ‘possible rewards’ also has the same strange red icon, so it might be worth revisiting this level later on to make sure that I haven’t just fallen victim to a bad random loot generator, but for now – time to push on.