A nightstalker's maw has a row of inward-hooking teeth on each side of the lower jaw and TWO rows on each side in the upper jaw. Their loose articulation allows them to work over and swallow prey wider than their head, including entire humans if the nightstalker is big enough. (The big poison fangs fold to let prey in. Yes, real venomous snakes do this too.)

Due to the many, many sharp inward-hooking teeth, it's almost impossible to pull back out once one starts eating you. They CAN voluntarily regurgitate prey by yawning so widely the teeth don't catch as the prey comes back up.

In theory anyway. 83