Mumble

The Mumble is an undead mummy. It can only attack if awoken, which in turn can only happen if one steps too near it.

Past
Assuming the Mumbles are actually undead mummies, these Mumbles were once humans, possibly the previous residents of the castle. At some point earlier, someone, possibly the Thing, wrapped the Mumbles in a cloth-like material throughout their entire body so that only their small eyes were visible. The rest of their body was a pale, white cloth. They were also set in a stage of hibernation in which they could only be awoken if a human stepped too near it.

The Thing
Once the Thing took control of the castle, the Mumbles were one of the many minions that worked for the Thing. They were placed in various places around the castle, such as in the Cemetery, the Barracks, among other places. If they saw any enemies of the Thing, they would hold their hounds out and slap the enemy across the face, which would significantly injure the enemy.

Bouapha
Once Bouapha entered the castle to get the brains back from the Thing, the Mumbles were ready to kill him. Once Bouapha came too close to the Mumbles, the Mumbles awoke from their hibernation and walked towards Bouapha, and were often able to injure him. They were also used to guard various keys in the Castle, and also to guard certain passages, as in the Barracks. In the end, however, Bouapha was able to kill many of them with his hammers.

Biology and appearance
Although the Mumbles were not low-intelligence animals such as the Aquazoid, their curious biology and appearance should be noted. The Mumbles could assumingly sense a person is near, and they could stay in a continuous hibernation without blinking or any of the sort. Their appearance is also unusual. They wore a pale white cloth that covered their entire body, except for their eyes. Their feet also had an extension on the rear of their heel.