A clear blue crystal orb with a 1" silvery pedestal engraved with animals looking in.
D&D 5th Edition Properties
On activation (maximum of once per day) which requires 1 action, choose a creature type with an average Intelligence score equal to or less than 3, like Zombies.
As long as the orb is active (it requires a bonus action to deactivate), all creatures of the specified type within 500' feet must come (at their normal speed) as close to the orb as creature density allows and stay there. There is no save for this.
If other forces, like an attack or a turn undead, influences those creature, they can respond as dictated, but will automatically return if they are still within 500' of the orb.