Spire of Iron and Crystal (2009)

From the publisher's website: "Difficult adventure for Swords & Wizardry Core Rules. Deep in the wilderness stands the legendary Spire of Iron and Crystal, a bizarre structure of twisting iron and four enormous crystals that seem to grow from the very ground itself. The fabled riches of the Spire have never been plundered, for no entrances have ever been found... Until now. Your party of adventurers has discovered the long-hidden secret of entering the Spire. Designed for 4-6 characters level 5-6. This adventure is being described as 'strange,' and 'deadly' by those who have read and played it."