Grinding zombie : how to use ?

[ronanry]

Basically the title says it all...
I went in a dungeon (the first one or rat lair, can't remember) i use the potion, and after a few second, it disappears
As i'm not an english user, i don't understand what means "a grinding zombie"
does that means that, it will change me into something else : like an auto(afk) killer ?
or does it improve the damage i made against zombie (in which case, i haven't found zombie yet :p )
or something else ?

[Qzhuo]

It should automatically move, hunt down mobs, loot destroyables, and descend to the next floor for you for 500 actions.

If nothing is happening, you're either in a boss room or it might be bugged.