Iron Maiden

The Iron Maiden is an obstacle, firstly introduced on American Ninja Warrior 9 as the ninth obstacle during Kansas City finals. On this obstacle:
 * Competitors have to hold on to a bar, then to a pair of hollow-shaped pegs and must place them to peg-shaped spikes while going down in the first panel.
 * Then, they must go up on the second panel using the spikes already placed in the panel.
 * Then, they must repeat the process they did in the first panel and must swing to the landing platform to advance.

Only two competitors attempted the obstacle (Mitch VeDepo and Tyler Yamauchi), with Mitch VeDepo being the only one who could complete it and later failed on the Elevator Climb, making Kansas City finals on American Ninja Warrior 9 just became the second city finals course in American Ninja Warrior history to have zero finishers.

American Ninja Warrior 10
On American Ninja Warrior 10, the Iron Maiden appeared as the ninth obstacle during Minneapolis finals, and the obstacle remained unchanged from the previous season, except the dismount being further down.

This time, the obstacle got to show its true potential, as a total of 16 competitors attempted the obstacle. Because of this, the obstacle became more brutal, as only 5 competitors could complete it (Joe Moravsky, Ian Dory, Jon Alexis Jr., Jake Murray, and Jonathan Stevens). Since 16 competitors could reach the obstacle, the Iron Maiden became the cut-off for the top 15 competitors to advance to Las Vegas national finals.

Interestingly, three of its victims on this season (Lance Pekus, Hunter Guerard, and Eric Middleton) barely missed out on attempting the obstacle during Kansas City finals on the previous season. This was due to the fact that all three of them failed on one obstacle before the Iron Maiden (the Floating Monkey Bars).

Northwest Passage
A variation of the Iron Maiden first appeared as the ninth obstacle during Seattle-Tacoma finals on American Ninja Warrior 11 and was named as the Northwest Passage. It was very similar in appearance and function, except for the fact that the obstacle's pegs had hooks going up that competitors had to use to climb up and down the panels.

During Seattle/Tacoma finals, the obstacle proved to be brutal, as out of the three competitors who attempted it (Karson Voiles, Jessie Graff, and Dan Yager), all three failed. The small number of competitors to attempt the obstacle was due to the brutality of both the Lightning Bolts and the previous obstacle, the Floating Monkey Bars, which knocked out more than 80% of the city finalists field. As such, Seattle-Tacoma finals ended up with zero finishers, making it the third instance in American Ninja Warrior history where no competitor was able to complete the city finals course (after American Ninja Warrior 8's Philadelphia finals and American Ninja Warrior 9's Kansas City finals).

Iron Summit
Another variation of the Iron Maiden (called as the Iron Summit) appeared as the second obstacle in Stage Three on American Ninja Warrior 11, replacing the En Garde from the previous season.

Upon closer inspection, the obstacle was considered as a hybrid of the Iron Maiden and the Northwest Passage, as there were similar specifications from those obstacle appeared.

Competitors have to first use the hollow-shaped pegs and transit to the hooks placed in slots to the top on the first panel and then do the opposite on the other.

In total, 20 competitors attempted the obstacle and 3 of them failed to complete it (Ryan Stratis, Nate Burkhalter, and R.J. Roman).

It was replaced in American Ninja Warrior 13 by the Stalactites.

Australian Ninja Warrior
On Australian Ninja Warrior 2, the Iron Maiden appeared as the fourth obstacle in Stage Three. However, compared to the one used on American Ninja Warrior, the obstacle featured:
 * only one panel and a pair of hollow-shaped pegs were used, and
 * a pole at the start of the obstacle, as a medium to reach the pegs.

Also, since no competitor was able to complete Stage Two on that season, the obstacle was unattempted.

Ninja Warrior Poland
On Ninja Warrior Poland 4 appeared as the fifth obstacle in Heat 3 and Heat 5. Contrary to the version from the American Ninja Warrior, there was a rope in front of the three pegged panels with which participants had to get to the first pegs. The length of each panel was 2 meters.

Competitors' Success Rate

 * All results based on the NBC broadcast and external information found

Trivia

 * The name of this obstacle is based on an ancient medieval torture device that goes with the same name.
 * The Iron Maiden was one of the eight obstacles that won the first edition of American Ninja Warrior: Obstacle Design Challenge, and designed by American Ninja Warrior veteran, Brett Sims.
 * The obstacle's function was the same as the ones used in a pegboard. But unlike a pegboard, competitors must use hollow-shaped pegs instead of regular pegs.
 * The Iron Maiden during American Ninja Warrior 10's Minneapolis finals became the fourth instance where the ninth obstacle became the cut off for the top 15 competitors to advance to Las Vegas national finals (meaning the previous obstacle, i.e. the eighth obstacle, had at least 15 competitors completed it). The other instances were during American Ninja Warrior 5's Baltimore finals (where the Body Prop became the cut off), American Ninja Warrior 7's Kansas City finals (where the Body Prop became the cut off once again), and American Ninja Warrior 10's Los Angeles finals (where the Baton Pass became the cut off).
 * It happened to be that in the first appearance of the Iron Maiden during American Ninja Warrior 9's Kansas City finals and the Northwest Passage during American Ninja Warrior 11's Seattle-Tacoma finals, both city finals courses had zero finishers and the Floating Monkey Bars was served as the previous obstacle.
 * The Iron Maiden during American Ninja Warrior 10's Minneapolis finals also shared several similarities with The Wedge during American Ninja Warrior 9's Denver finals:
 * Each of those two obstacles had 16 competitors attempted it, meaning both of the obstacles became the cut off for the top 15 competitors to advance to Las Vegas national finals.
 * Every competitor who attempted either of those two obstacles advanced to Las Vegas national finals. This was due to the fact that Meagan Martin attempted both obstacles and later finished in 16th place during both city finals rounds. However, she still advanced to Las Vegas national finals via the top 2 female competitors.
 * Both obstacles were in a course that had a ring-oriented obstacle in the course (the Ring Swing in Denver, and the Sky Hooks during Minneapolis finals, coincidentally replacing the Ring Jump, which was used during Minneapolis qualifiers), as well a balance or lower-body oriented obstacle in the fourth spot.
 * Both obstacles also wiped out Karson Voiles and Drew Knapp.
 * With Karson Voiles, Jessie Graff, and Dan Yager all attempting and falling on the Northwest Passage during American Ninja Warrior 11's Seattle-Tacoma finals, this marked the first time that the ninth obstacle during city finals round had a 0% completion rate, since American Ninja Warrior fully featured 10 obstacles in every city finals course (starting on American Ninja Warrior 5).
 * This also marked the first time ever that the final obstacle in a city finals course was left unattempted.