The Halls of the Mad Mage

From the introduction:

The archmage Callisto once claimed to have “conquered the insight of the seventeen quasi-dimensions of the elder lords of Oud”. It was not long before he had become known as the Mad Mage. But perhaps there was some method in that madness: His long-abandoned sanctuary – inhabited now by his former slaves and arcane experiments – is a place where space is contorted impossibly upon itself.