Blood leaked alpha - jcastlek (full level walkthrough)
jcastlek is a map that appears in the leaked Blood alpha, but was removed from the retail game.
This appears to be a variant of jcast1b. While enemy and architecture is the same as that map, the item layout is quite different. Some examples include the first sawed off shotgun being in front of the room that releases four axe zombies when you get near it instead of on the left "shelf" when you first enter the u-shaped stairway, no ammo and health in the fountain area, and the cut alternate flare gun ammo being replaced with TNT crates.
jcast1b was last modified on January 6th, 1996, but jcastlek was last changed on January 8th, 1996.
The j in the level's name is likely a reference to James Wilson III, who designed several maps in both the prototype and the final game. One of the maps in the prototype with "j" as it's first character has James Wilson III defined as the level's author, meaning this is probably the case.
I'm not sure who the "k" stands for, but it could be for Keven Kilstrom, who made several levels for Blood. Supporting this is that some levels made by him in the final game appear in the prototype with "k" as their first character.