The Zruty is a rather peculiar monster native to NetHack. To the best of my knowledge, it was incorporated in order to have a monster that actually started with "Z", since the various "Zombie" monsters were classed by their previous existance (I.E. Elf Zombie).

The Zruty is of neutral alignment and appeases your god by 1 point when sacrificed. It is level 10 and has 44 hit points and an armor class of 3. There is nothing particularly special about it, and it is described as a large, non-descript quadroped.

It is a rather embarassing experience to be killed by a zruty, largely due to the history behind their existance.