Sword of Fargoal certainly the game I think of when I think C64 dungeon crawler :)

But apparently it wasn't written just in BASIC for the C64 version. From Wikipedia:

> The following year, with the release of the Commodore 64, McCord was asked to release a version of Sword of Fargoal for that machine as well. McCord was unable to implement the conversion as it was written in BASIC, and the sprite-based graphics required machine language programming. McCord's friend Scott Corsaire (then Carter) and Steve Lepisto wrote all the machine-language code that was needed so that game would perform fast enough to work on the Commodore 64.

What amazes me is that, apparently, most of Sid Meier's Pirates! was written in real C64 BASIC. It boggles the mind. Back when I was a kid I loved my C64 I thought it had the most useless BASIC ever, I envied what I thought was a better version in the Speccy. If only I had known what could be done with this...