Sentinels of the Multiverse is a card game about a team of superheroes battling a supervillian. It was originally released as a physical set, and later adapted into a computer version. I picked it up in a recent Steam sale, and it's also available on iOS and Android.
The characters and art are very much in the Silver-Age comic style. It's all specific to the game, not based on any existing franchise, although many of the characters are very familiar. Wraith has a lot of Batman characteristics, Legacy is like Superman, etc.
The villains are much stronger than each individual hero, plus the environment tends to cause more problems for the heroes. Therefore, teamwork is essential. I've been playing Sentinels of the Multiverse solo, which means I control all of the heroes myself. You still have to play their turns one at a time, but there's no danger of someone going off in their own direction...unless that's what you want, of course. I don't really plan to play the game with random online folks, but a few of my friends do have it on Steam, so maybe I'll be able to organize a game with them at some point.
The gameplay itself is pretty simple. On each turn, a hero gets to play a card from their hand, use a power from a card in play, and draw a card. There's lots of synergies between the heroes, so often one hero's turn will set up another hero to make a big hit on the villain or otherwise boost their abilities. The villain and environment each get their own turns, playing a card from their deck and/or using abilities on cards they have in play. If the heroes drop the villain's hit points to zero before each of theirs fall to zero, they win.
I very much like the cooperate aspect of the game. There's not really any "winner" of the game as such - either you all win as a team by taking out the villain, or you all lose when the villain knocks out all the heroes. Playing as a single player that doesn't matter much, of course, since I control all the heroes anyway. I've played similar team-vs-the-game setups with multiple players, though, and I like the cooperative aspect.
There are two major shortcomings to Sentinels of the Multiverse, at least for me. First, the balance is pretty uneven with different initial setups. Playing with three heroes might be really tough, but adding a fourth or fifth makes it extremely easy. Some heroes have very little actual attack power, so picking a group comprised mostly of those can make the game nigh-unwinnable. I'm sure experience will help to avoid those situations, but it can be pretty discouraging for a newer player.
Second, there's very little to the game outside of playing individual battles. You fire up the game, win or lose against a villain, and that's it. Back to the main menu, with nothing changed. That's not a problem for a physical game that you'll only play once a month with friends, but for a video game it means players likely won't come back after their first few attempts. A little web searching told me that there are achievements and the ability to unlock variant versions of some heroes, but those aren't obvious in the game itself. There is also a weekly "one-shot" challenge, where you have to win some particularly difficult initial starting setup, but that's tough for newer players (plus some of them aren't playable without buying added content). Some kind of single-player campaign, with a few battles that gradually ramp up in difficulty, would make for a much better experience for the beginner.
I've been enjoying discovering the different combinations of heroes and villains in Sentinels of the Multiverse, and I'll probably keep it around the Steam library for a while. It has its flaws, but overall it's a fun way to enjoy the occasional comic-book style battle.