Code named "Project Test Three", Herbert is the main antagonist of Beyond Closed Doors. He appears briefly in Chapter 1 and roams around the Cave in Chapter 2, hunting for the player. According to Dr. Naoma (see page "Scientists"), "[Herbert is] a highly aggressive monster and has to be tranquilized unlike the other entities. He has four arms, an obscure, alien-like face akin to classical horror movies, and is about ten feet tall. We located him deep in a nearby chasm, feasting on what seemed to be animals, which we weren't able to identify. The fiend walks on four legs from time-to-time, has a hard, beetle-like shell, and white bone-like protrusions on his chest, which is assumed to be his rib cage. The entity is determined to be four hundred-fifty pounds."
Credit goes towards VKS
The Leecher was a failed experiment, hence being tossed away in the Cave (see page "Setting"). This zombie-like creature likely launches some sort of tentacle parasite to hunt down absorb its prey. The tentacle would then travel back to the Leecher and await new commands. The Leecher has yet to appear in-game.