Buried Skeleton

This idea is meant as a supplement to potential upcoming structures.

Imagine exploring a dank crypt and suddenly, all around you, skeletons emerge from the ground, surrounding you and closing in. This is what this mob is about.

This hostile mob is created in limited amount (doesn't spawn) within the ground, during the creating of a fitting structure. It emerges either when the player comes very close to it, or when other buried skeletons in the vicinity emerge, which can cause a chain reaction.

In order to give the player a fair chance, a small part of the skeleton sticks out of the ground, and it can be already attacked. Which of course will also cause it to emerge, but allows the player to prepare.

I imagine it looking just like a regular skeleton, but as it ambushes, it uses a melee weapon rather than a bow. It also might come with armor. But the exact configuration and appearance is not what the concept is about. This would also work with something entirely different, like a buried scarab.