Not OP but Marvel makes an API available for all this so most of it's likely within bounds:

http://developer.marvel.com/

They may have a problem with the use of "Marvel" in the domain name though.

Yeah, the terms & conditions say you can't have "Marvel" in your name:

"You may not create derivatives of Marvel Property, or use the 'Marvel' name or any other Marvel Marks in the title of your App without Marvel's prior written approval."

They might let you if you ask, though. It's not like it's a commercial app.

I think it's good that you added links back to the Marvel website, and attributed the data to Marvel, following their guidelines: http://developer.marvel.com/documentation/attribution

Some developers overlook the boring API documentation and rules.

I have reciprocal links going back to marvel.com, there are no ads and I did receive a feedback from an individual on Marvel dev team that he liked the app. So I'm assuming they are cool with it.

> assuming they are cool with it

That reception is probably not uniform among Marvel, especially since they have to mount an affirmative defense against trademark infringement. But just don't get too popular and it will never matter. ;)

I'll try not too :)