It is copyright infringement when a list of public domain characters from a video game is used in another?

It gets tricky, because the character itself might be public domain, but the specific representation of the character may not be.

There's also the issue of the fact that you may be right, but still not be able to afford to prove it.

A lawyer would obviously be able to provide more details if they knew the specifics, but it really depends on the context and what exactly is being replicated.

Not a lawyer, not even close, but I'd be a little weary of using the exact same list.

A list of things with no creativity involved won't fall under copyright, but the argument would be that they exercised creativity in curating a list of those specific figures. They could probably argue it and succeed. But since they're pulling from the public domain, I doubt they'd go after anyone on it.

Would definitely be a problem if someone bases new things on designs from that game. Derivative work from public domain work still gets copyrighted, right?

If they use original art, no, even if the characters are owned by a company.

It may be trademark infringement, however. Depends on how close you get. See Spirt Halloween costumes for examples.

Age of Mythology has a lot of gods from various religions. I havent seen Microsoft sue Marvel over it though

In SMITE's case, the characters come from mythological sources and those sources are public domain. However, the way they're depicted was chosen by the game developer and their depictions are copyrighted by them.

If someone copied the list of characters and made their own game with their own artwork and gameplay and everything, SMITE's creators could do absolutely nothing about it. But if they copied any substantial elements from SMITE directly, then it starts to go in the direction where lawyers start rising eyebrows. At that point it's no longer making original stuff based on the same PD material.

Not a lawyer, but I've had to deal with copyright before. If I'm not mistaken, the only thing the Smite devs could feasibly hold a copyright to is there specific expression of the characters - i.e. the unique visual design, the voice lines, the lore (assuming it's not also just the lore from already existing public domain works), animations, etc., that's the only time you'd be in trouble. With game mechanics it's pretty dicey because I think you'd have a hard time finding a judge to actually rule that any company "owns" a game mechanic. But if you copy how the characters look, the art style, maybe even specific dialogue (which couldn't be found as part of another public domain work) that's when you could possibly have a claim.

But even still, you have to remember that copyright is not this "oh you've broken the law you're a criminal now" type thing where once you've "infringed" it's over. It's typically handled first via informal means like contacting Steam/Epic/GOG/etc. and saying "hey we believe these guys have stolen our character." They'll have to convince the platforms first, and then the platforms will take it down to avoid liability. It's only if the parties want to pursue it further will they have to take it to court and have a jury/judge rule on it. Copyright suits tend to be ruled on precedent rather than just the black-and-white letter of the law.

I saw Sun Wukong in both League of legends and Dota 2.

Assuming you're referring to U.S. law, I'm not a lawyer, but if a character is in the public domain, they're available for anyone to create new material with. Using the same list of characters in a different game/story that's your own creation should be fine.