Seventh Doctor companion Ace was a very 1980s kind of a companion. Her name made her sound like a cartoon dog from Saturday morning kids' TV, she wore a fairly hideous nylon bomber jacket, and had a very intense relationship with high explosives, most notably her beloved Nitro-9. Alas, it was to be her undoing: in the Doctor Who Magazine comic Ground Zero she was revealed to have explosively disembowelled herself with the stuff. That said, Ace seems to exist in about fifteen different timelines at once, so technically speaking she's still roughly fourteen-fifteenths alive. Clara's not very explosion-friendly but given her importance to this Doctor in particular, it only seems right and proper that she take half of Shoreditch with her in a properly spectacular fireball when she does eventually go.