Edit 404 page for Magazine theme?

[polybius]

Where do you edit the 404 page content for the Magazine theme?

The 404.html isn't used.

[Harm10]

What page is set in your configuration to be used as 404 page?
This is in the common settings of your installation.

[polybius]

What page is set in your configuration to be used as 404 page?
This is in the common settings of your installation.

It's the default first option, labeled "Page 404 par défaut", the two other options I have are links & about.

I had a look around, but couldn't find where the theme pulls its 404 page and text, it looks like its themed as an entry page though, with a 404 texte in it (but not the 404.html text).

[Harm10]

If you have that setting then the default html page is used. This is located in the templates folder itself and called 404.html.
If you want to customize it than create your own version in your template folder and give it another name.
The customized version will show up in the selection.