Above the roars of the masked figure Yaz heard a terrible scream. It wasn't human, or anything resembling it. It was higher pitched. It froze the blood.
"AN INTRUDER!" the masked figure roared. WHO DARES TRESPASS IN OMEGA'S DOMAIN?"
Yaz's head was pounding as he spoke. It was hard to think when someone was talking in that way and they weren't even taking the mickey.
"It's the Ergon," Yaz shouted over the din. "It wants to kill us both!"
"IT IS NOT THE ERGON", chided the figure. "IT IS ONLY AN ERGON. ONE MADE BY A TERRIFIED CHILD. IT WOULD TREMBLE BEFORE A CREATURE BORN OF THE MIGHTY OMEGA"—
"Omega said his Ergon was rubbish," Yaz shouted, if only to stop the figure talking.
"RUBBISH?!" the voice bellowed, and she instantly wished she hadn't said anything.
"HE HIS FORGOTTEN HOW GREAT HIS RAGE ONCE WAS," the voice went on. "HOW MIGHTY IT CAN BE!"
The eyes of the mask began to gleam pure white.
"HE WILL NOT FORGET NOW," the mask boomed from its glowing mouth. "NOT EVER AGAIN. LOOK UPON HIS ERGON AS IT TRULY IS. MARVEL AT THE APEX OF HIS RAGE!"
"Run, you idiot," said a voice in Yaz's head. But as she got to her feet the figure's mask had slammed upwards, its face now pointing up to the crumbling roof. Its spiked chin was now a beak, its eyes now flaring nostrils. Jagged wings of silver and gold were scissoring out of the cloak, and as Yaz started to flee she saw the whole creature burst free.
It was true, then. They were more similar than she had known. Behind her she heard Omega's Ergon let out an awful, metallic cry. And there was another cry in response, and a sound like both feathers and fury was keening behind her as she ran.
The Doctor's Ergon was here, too. But that didn't matter. It wasn't worth turning round. Survival was the only thing that mattered now. Keep running forward. Never look back.
An enormous piece of masonry crashed down beside her, missing her side by inches. She could feel something deep inside herself screaming; her training was ebbing away.
And something else was going wrong inside her. A feeling like pins and needles only worse; like she was a Yaz-flavoured bath bomb fizzing into nothing. The Doctor had said they couldn't remain here for long. That her antimatter would flip back into matter, and then she'd die. They both would, for a reason that was silly and was stupid.
But you kept going on. You didn't break. She didn't know where she'd learned that, but she had.
As the castle collapsed all around her, she ran for the chaos outside.