The Basilisk Lair was introduced to the game at the same time that Cinder Caldera (Giovanni's realm) was introduced, in December 2014. I'm not sure at what level the Basilisk Lair will become available to new players in the game, so if you happen to know that information, please hit me up via my Facebook page (link at top left) so I can fill it in!
Similar to the Squash Patch, the Basilisk Lair produces two different items: Basilisk Scales and Basilisk Tears. To find out more about these items specifically, such as their pricing and the recipes in which they're used, check out their respective pages (linked in the previous sentence).
5 Basilisk Scales (every time)
1 Basilisk Tear (randomly on occasion)
Available to buy at level:
First: 4,000 royal coin, 30 crowns thereafter
Time to build after purchase:
Maximum number per kingdom: