De-Powering the protagonist is a common trope in books, comics, and especially videogames. One could argue that just weakening a protagonist counts as a form of this, and it therefore shows up even more as a way to up the tension and drama in a story. However, in a table top RPG you need to be more careful with it. Today I want to talk about that, ways it works, and why you want to be careful.
Who Are You Without Your Powers?
The theme behind de-powering characters tends to boil down revealing who they are without their powers. This can be done as a test like in Thor, or just as part of the narrative or character development as has been done in several Iron Man stories and other works of fiction.
What does the hero do when they don't have their magic sword? Their invulnerability? Their suit of power armor? Do they run and hide? Do they still try to stand up to the villain? It's an affirming moment for the character that their heroism is more than because of their usual means of performing heroics, it's a part of who they are, and it can be a big moment. Which is why it wouldn't be surprising, especially in a super hero game, if you wanted to do it. Right?
How to De-Power
There seems to be three main ways to de-power your heroes depending on the source of their power.
The first is used a lot in Super Hero games. Something happens - an alien ray or a nullifier gun - and all the hero's powers simply don't work. Spider-man suddenly can't climb on walls or sense incoming danger. Superman can't fly, and is no longer strong or invulnerable. You get the idea. The solution then is either the hero eventually reverses the ray or thing that stole their powers, or their powers just come back on their own. For a game, I'd recommend the former, but that is up to you.
The second is like the first, but works with heroes who get their power from an item. For this you simply take the item. Tony Stark has no access to the Iron Man suit. Blade has no access to the crystal needed to transform into Tekkaman. The Paladin no longer has their Holy Avenger or magical armor. These can be stolen by the villain, in which case the hero needs to get them back, or from some higher power ostensibly on the PC's side as a test
The third one is for heroes who are more 'normal' and it's pretty simple. You hurt them bad, and then put them in a situation where they have to act without being able to heal or treat it. This one is super dangerous in table top RPGs because hurt PCs are a lot easier to kill, especially on accident.
Why Is It Dangerous
If this trope is so common in fiction, why is it dangerous in games? Well, because of how it works. In fiction the author has control of the story. It's a way of heightening tension and drama, but there is no RNG that will go "and because the Paladin didn't have their +4 sword they missed and were skewered through by the death knight." In a game that could easily happen.
The other problem is you are effectively taking away the 'toys' the PCs have earned or built these characters specifically to play with. The longer they go without those things, the longer they go with only part of what they made the character to do and their particular desires for the character.
This doesn't mean you can't do a de-power arc. Just don't over do it, and make sure you have a quick, firm resolution for the plot. Get your tension, but get the PCs their stuff back too and give them time to enjoy it before you even threaten it again.