The Iron Maiden (named after the medieval torture device) is a variant of the Regenerador from Resident Evil 4. The two creatures are the same in almost every way, but the Iron Maiden has the additional feature of multiple spikes growing all over its body. When engaging an enemy, the Iron Maiden's preferred method of attack is to stretch out its arms and pull its prey towards it, impaling the victim on the many spikes that extend from the body.
Leon Kennedy encountered a number of these B.O.W.'s during his investigation of Osmund Saddler's island base. Like the Regeneradores, Iron Maidens can rapidly regenerate any injuries and the fastest, most efficient way of defeating them is to target the leech-like Las Plagas in their bodies with a sniper rifle equipped with an infrared scope.
In the 2023 remake of Resident Evil 4, some Regeneradores will suddenly transform into Iron Maidens after the Plagas in their bodies have been destroyed. A new Plaga core will form inside the creature's head as spikes extend from its body. The creature remains just as difficult to kill as before, but with the added threat of immediate death by perforation upon its spikes. Even when the creature dies, it can still potentially kill the player as its spikes spray in all directions when its body explodes.