The interior of the skull was vast enough to swallow cathedral.
Pulling himself through the opening at the base of the neck, Nero found his body screaming in protest as he scraped against the bone edge. His broken arm still dangled uselessly and his injured leg threatened to give out with every movement so it was not a very pleasant experience.
Even worse, the Mark of Mephistopheles had continued its steady throb of agony once again, further cementing his rather bleak condition.
When he finally hauled himself into the skull proper, he froze.
The walls were covered in runes.
Thousands of them, perhaps tens of thousands, carved into the bone with shockingly painstaking precision. They glowed with a soft, pale bluish light that illuminated the cavernous space, casting everything in shades of cold illumination.
The symbols were intricate beyond comprehension, spiraling and interconnecting in patterns that made his eyes hurt just looking at them peripherally.
