Does this have a campaign?

Not really. It has a bunch of scenarios/challenges tho.

It's a board game about building your civilization and compete against the AI or multiple AI. Also you can play MP, but I don't know much about it.

It does look interesting. I like these kind of board games, so I'll keep it in mind.

Thanks for the suggestions.

Very welcome! :)

Card Hunter has most of the game for free, single player campaign + extra scenarios as challenges + multiplayer battles/tournaments. You control 3 characters (dwarf/elf/human warrior/wizard/priest any choice/combo) on a map with squares, your equipment is practically your deck, each piece of equipment adds 3 cards to the deck, and you fight against enemy monsters with the goal of killing them all or conquering victory squares. Very fun and big variety of gameplay.

Surprised no one's suggested Yugioh Legacy of the Duelist, or any other Yugioh game.

Shovel Knight: King of Cards. It's a platformer first and foremost but it has a card game within it, and it's not a mini-game or some afterthought addition, it's the whole reason for the plot/game. It may look simple at first, but the further you progress, the more cards/mechanics/abilities the game gives you. It's a really unique card game and surprisingly addictive. I highly recommend it. It's here of GOG and I'm pretty sure you can buy it and play it without needing the other Shovel Knight campaigns. But all of Shovel Knight is super fun too so I recommend that as well if you want a well-made and delightfully charming action/adventure platformer. Hope that helps!

In my opinion, two games stand head and shoulders above the competition:
- Etherlords II (has a long campaign)
- Slay the Spire (No campaign, roguelike, but superb mechanics)

I've spent upwards of a 100 hours with each of them.

What about 1?

One is also good, but not as good as 2. I'd say E1 is 8.5/10, while E2 is 10/10.

E1 is like HOMM in that you have discrete maps with castles that you have to protect, which dilutes the CCG element. They did away with that in E2, so it's more like King's Bounty The Legend, one long continuous campaign (actually two long campaigns, each with 12 maps and 160-190 card battles), except that the battles are card-based.

You don't have to play E1 before E2.

Thanks everyone for your recommendations.

Thanks. I got both already, so will give them a try.

Sorry, but it's nagging me that I forgot this one (because for some weird reason, I forgot to tick the card tag), so just real quick:
Deek Sky Derelicts: https://www.gog.com/game/deep_sky_derelicts; Deluxe Edition: https://www.gog.com/game/deep_sky_derelicts_definitive_edition
In Deep Sky Derelicts you get to pick some cards when a character levels up, but most of the time you will decide about their decks by changing their equipment.

Card City Nights is the closest to "single player CCG". In game, you literally build decks from your collection, go around, and do battles to progress and earn more cards.

But tons of other games listed in this thread have great card-based resolution mechanics. Slay the Spire is a "deckbuilding game" rather than a CCG, but ABSOLUTELY do try it. It is one of the best card-based games out there, whether tabletop or electronic.

Just finished this game (well, the main storyline, I see there is more after you finish the campaign), and I can't thank you enough for recommending it. What a nice gem.

Played nothing else last few days and now I see those cards in my sleep.

Too bad the sequel is not on GOG, but I got it during Steam sale.

I so wish there was a physical version of this.

Glad, that you like it. :-)
It has tons of charm. I replay it every once in a while and still hope the sequel will get here eventually.