Poky

Pokies are invulnerable enemies that slide around the room aimlessly in cardinal directions, dealing contact damage. They may move slightly faster towards Isaac if he gets in their sight. When the enemies or Silver Buttons are cleared from the room, the Poky stops moving and no longer does contact damage.

Slide
Slides will remain stationary in their positions and have their spikes drawn out, dealing contact damage. Should Isaac get in their sight in a cardinal direction, Slides will move towards Isaac's direction, then move back to their previous position after hitting a wall or obstacle. They have a short cooldown after charging towards Isaac before being able to move again. They will not stop moving even after enemies in the room are cleared. They can, however, be deactivated by Silver Buttons and retract their spikes as a result, meaning that they'll stop dealing contact damage and also stop moving towards Isaac.

Wall Hugger
Wall Huggers move around walls and obstacles endlessly. A couple of seconds after Isaac enters a room with them, their spikes will be drawn out, dealing contact damage. They cannot be shut down, even if enemies are cleared from the room. They can, however, be deactivated by Silver Buttons, retracting its spikes, meaning that it'll no longer move and do contact damage. Their paths can also be stopped should a fireplace or static enemy be in their way.

Grudge
Grudges are exclusive to and  and are characterized by the eye in the center and two spikes on each side instead of three. They remain stationary until there's an uninterrupted path between it and Isaac in a cardinal direction, at which point it will quickly slide towards him, dealing a full heart of damage if it hits. They will not return to their original position after moving. They also have unique interactions with other stage elements.
 * If it runs into an enemy, it will be pushed along with it, instantly killing it if they're caught between the Grudge and a wall/obstacle.
 * Even bosses are prone to this instant kill effect. However, the only method to witness this happening is to get a effect with summoning friendly Grudges.
 * If it runs over a Button, it will be pressed. Many rooms use this to create puzzles where Isaac has to manipulate the Grudge into pressing buttons.
 * If it runs into a bomb, it will be pushed along with it, causing it to instantly explode if it gets caught between the Grudge and a wall/obstacle.

Grudges can be instakilled, but they will respawn upon re-entering the room.

Trivia

 * The three original variants are similar to Blade Traps, hazards found in The Legend of Zelda, with each trap imitating the different behaviors of them between games.
 * Pokies imitate the Blade Traps from Phantom Hourglass and Spirit Tracks, being traps that move freely around the room.
 * Slides imitate the traditional Blade Traps from the original The Legend of Zelda, charging towards Isaac whenever he is in their line of detection.
 * Wall Huggers imitate the Blade Traps from Twilight Princess, moving around the room's walls and obstacles.
 * Isaac has a unique gibbed death animation if he dies to a Grudge.