Iron Maiden

Iron Maidens are apparent Regenerador variants/prototypes; large humanoid creatures well above a normal human's height. They share most physical traits with the Regenerador but with slight differences; they have a larger mouth that takes up almost their whole face, have a purple hue to their skin and many large pointed spikes and nails protruding from their bodies. Their name comes from the ancient torturing tool, the Iron Maiden, which was a standing coffin of sorts filled with sharp spikes on the inside which you would lock victims into.

Much like the Regeneradores, they can be shot several times with no effect and their lost limbs will regrow in a matter of seconds, even the head, and they house several leech-like Plagas as well. However, the Iron Maidens lack visible eyes and have a slower walking speed than Regeneradores but can crawl much faster. The Iron Maidens tend to use their spikes as weapons, having a special attack where they grab Leon, pull him toward itself and then extend their spikes, impaling him for massive damage. They do not use their mouths to attack due to it being severely deformed (it has a mouth similar to the Gravedigger). They walk in a slow, deliberate manner, constantly suffering from rapid, spastic movements. When dying, their upper torso erratically launch the spikes adorning its body.

Role in Resident Evil 4
The Iron Maidens fill basically the same role as the Regenerador, although they are encountered much more rarely; they are so rare, in fact, that only three Iron Maidens are fought in the entire game.The last two (fought in the same area) drops 30000 Pesetas upon their death.

Lab Room

Leon first encounters an Iron Maiden shortly after entering a research lab on the island when you see the beast lurking into a door through the cameras. The first Iron Maiden holds a key-card necessary to open Ashley's cell, possibly placed there to deter Leon's progress. It is advisable to go into the room before the Iron Maiden to give you space from it. Take the opportunity to snipe the hidden Plagas' in its body before it gets close. There is another way to get to this Iron Maiden instead of looking through the Security Camera. When you walk into the room before the Security Camera Room, there is a glass window. Shoot that window and it will trigger the Iron Maiden to come out.

Garbage Disposal Area

After you jump down the Garbage Disposal and a cut scene occurs and you notice Ashley landed on an Iron Maiden, you know trouble is occurring (if you take out the infrared scope and zoom on the Iron Maiden you can still see it's giving off heat; it's not dead) After you open the first lever a cut scene occurs where the Iron Maiden comes back up. Ashley is able to hide in the Dumpster, and Leon has the advantage of being able to close gates down on the Iron Maiden, stalling its advance; however, do not think that the Iron Maiden will be unable to pass; it can still open the gate after a period of time. After being killed, the player probably is hoping there isn't another one. After pushing the crate into the water and walking farther over another Iron Maiden comes out. It is easier to go back to the gates and kill it there; it will give you time to stall. Or you can lure it over there and go out the door.

In the garbage disposal area, do NOT try to get to the second garbage bin (you must push a heavy box out of the way with Ashley's help) and attack the first Iron Maiden from there; the second one, hiding in the nearby hallway, will definitely sneak up on you and attack. Instead, dispose of the first Maiden before you move the box, then you can deal with the second one without being attacked from behind. Also, there are flammable barrels by the gates. You can use those to kill the Plaga on the back of the Iron Maiden.

Due to their lack of mandible usage, the Iron Maidens lack perhaps the Regenerador's strongest and most lethal attack, the shoulder-bite. Instead, they will try to grab you, then pull you into a "death-hug", impaling Leon on their spikes. Unless you have a large amount of health, this attack will almost always cause death, particularly on Pro Mode. The deadly "jumping bite" that the Regeneradors use to give an excellent effect is replaced with the Iron Maiden repelling its spikes, which deal medium damage.

Strategy
Despite its enhanced nature, Iron Maidens should be engaged using the same methods as a standard Regenerador, albeit with a greater caution as the distance between Leon and the Iron Maiden closes. It should also be noted that Iron Maidens possess a hidden Plaga on their back. The only way to get it is to shoot one of the legs first, then after they fall the plaga is visible to shoot.

It's also a good idea to carry around an grenade when you have to face these guys. This is because they always have a plaga on their back. If you shoot the 4 plagas on the front, you can deploy one of these grenades to finish it off.

In the waste disposal, (after taking out the first Iron Maiden), it is also possible to shoot the back plagas off the second through the chain link fence without blowing off any of it's legs or using incendiary grenades. Instead, push the dumpster into the water, then walk back to the chain fence, and you will see the Iron Maiden standing on the other side, unaware of your position, and with it's back exposed, revealing the plagas. Once eradicated, this will allow the player to concentrate on the frontal plagas without the need of removing a limb or the use of an incendiary grenade.

Use extreme caution if Ashley is with you, she is vulnerable to its attack and she will have trouble avoiding it.

Same as Regeneradores, Iron Maidens will leave behind a Pelvis if they are killed while missing both legs, and will leave a large amout of money.

Trivia

 * The Iron Maiden and the Regenerador have been consistently rated by video game websites to be one of the scariest creatures in Resident Evil 4.
 * Despite being stronger than their Regenerador counterparts, Iron Maidens have about the same amount of health when you kill them without using the rifle, magnum, or other penetrating weapon to attack the Plagas directly, and they sometimes have the same amount of the weak points seen through IR scope.
 * To get through open windows, an Iron Maiden "slithers" across it (whereas Leon would just jump through it). This can only be seen with the first Iron Maiden in the research lab area, by breaking open the window that connects two of the rooms in the area and then watching the Iron Maiden travel through it (if timed well, a skilled player can shoot the Plagas from its back without having to shoot its legs first while slithering in. Do back off, though, since it will get up rather quickly).
 * An Iron Maiden (or Virgin of Nuremberg) is an early-modern representation of Medieval torture devices, being in the form of an iron or wooden coffin tall enough to enclose a person, filled with strategically-placed spikes. Interestingly enough, if an Iron Maiden grabs Leon at full health and expands its spikes on him, it does not instantly kill him rather put him in a near death state. There is also an English Heavy Metal band of the same name.
 * Although never announced, the Iron Maiden's height is probably close to 6 feet 6 inches (same height of the Regenerador) based on its comparison to Leon.
 * If you have looked at an Iron Maiden closely, it has no eyes and has spasms when it walks, unlike Regeneradores. Also it has spikes, if you dodge the Iron Maiden while it's trying to get you, it'll actually show anger by making its spikes flex.
 * The Iron Maiden greatly resembles the Ooze of Resident Evil: Revelations.
 * Iron Maidens move slower than Regeneradores, almost limping towards the player.
 * If the player evades the first Iron Maiden by opening the door to the Radio Tower, when they return, the iron maiden will be standing very still, taking no notice of the player until they approach or shoot it.
 * The Iron Maidens are the only B.O.W.'s encountered in Resident Evil 4 whose name is not translated into Spanish.
 * The first Iron Maiden who hold the card key where ashley being held is the militia ganado who hold ashley in the first time in island.