- For other crypts, see crypt.
The purpose of the crypt is unknown - it may be a playground for developers, a testing site of sorts, an unfinished instance, or something else entirely. It is interesting to note that using WoW Map Viewer you can see that the crypt runs under Tranquil Gardens Cemetery in Duskwood. This might play a role sometime in the future, or could be a complete coincidence.
This area used to be accessed via dying close to the gate and running through it, but this was changed in Patch 2.0.
This section concerns content exclusive to Legion.
In Legion the Crypt is still inaccessible. However, an update was given. These include a gate and an altar. The crypt simply called "Crypt", has been renamed to "Forgotten Crypt".
Some people speculate that is a lower portion of Karazhan, as some lore indicated Karazhan has a mirrored lower half. But the architecture does not seem match with Karazhan in the slightest bit, leaving a rather large flaw in their speculation.
Reasons for abandonment
Many players suspect that the crypt was never fully implemented because the mildly disturbing content, mainly the now infamous room of upside down sinners, would've made World of Warcraft's ESRB rating become M for Mature. On January 24th, 2014 Blizzard community manager Bashiok responded to a post inquiring to the reasons the crypt was never used and provided some insights on Blizzard's design processes back during the days of it's creation, stating the reason it was abandoned was more than likely that Blizzard simply changed their minds about using it.