In the Dave Arneson Campaign Sourcebook p 148 there is a reference to the Irfat clan of the Peshwah and how the Irfat guard a place called the Crypt of the Horselords. This is an ancient underground burial place of all the Peshwah. It is located below Naktok and is a series of secret catacombs and tombs devoted to Raelraltataen.

Was this place ever explored in other Blackmoor material or in the MMRPG?

It sounds like a great potential for developing a megadungeon if you want one!

-Havard

Interesting find. Could be like a Barrowmaze kind of place.

So far I haven't encountered it yet in the MMRPG, but I have still many adventures to go through.