The Broken Cage

I was young and stupid once, believe it or not... thought the same as many other adventurers. Labyrinths were vaults, full of treasures ripe for the taking. Then I stumbled upon The Broken Cage. I've seen some things in this world I would call wrong: a child with haunted eyes, a slaughtered village left to rot, the death of an elven High Druid. I've lived through and experienced more terrifying things than I had any right to. Nothing and nobody has sent a chill down my spine like walking into that room. I tell you true, I don't know what the Forgotten Gods locked in that circle, and I don't never want to, but we had best hope whatever it was is dead and gone from this world.

— Jasper Cameron, Leader of the Bronze Ravens

What appear to be solid lines are, according to several former researchers, wizards and clerics, actually script and runes, written so small and packed in so close that they must be magnified by several orders of magnitude to even start to study them.
Notice the key word former. Everyone who has attempted to study the Broken Cage, or spent more than a passing amount of time in the room it is in, has gone completely insane. Maze Walker and Bet have re-sealed the room at lest 4 times over the millennia in an effort to protect people. But alas, as they say "you can try to make something idiot proof, but nature can always make a better idiot."
Known casualties:

• 2 powerful warlocks have attempted to commune with their patron to divine the contents of the room or the nature and workings of the containment spells, both died almost instantly.
• High Cleric of Tenjin attempted to use divine magic in the study of the room. "Smited" I believe is how his demise was described.
• On no less that 11 occasions spellcasters have attempted to consult the Abyssal powers on the room. Any creature summoned took one look around and promptly killed itself and in most cases the summoner who called it. The most spectacular case was a balor summoned inside the room. It promptly cast a death curse using its own True Name and burning its life-force as magical fuel. We only know this because it has been confirmed that a balor's name was burned out of the Demonomicon (all three copies) at roughly the same time that an entire expedition went missing and a forest fire started in the area due to "a storm of green lightning."