Basically when humans spent too much time too close to the star they got burnt alive, and because of wibbly wobbly timey wimey stuff the burnt Clara and "salvagers" were trapped in a time loop on the tardis which would explain why they were attacking, because presumably they were trying to kill their earlier selves in a less horrific quicker manner.
If you can fill the unforgiving minute,
With sixty seconds worth of distance run,
Yours is the Earth and everything that's in it,
And - which is more - you'll be a man my son.