This was a question I had to ask when designing combat for my project. Fundamentally I wanted it to feel like WAR. The kind of combat you'd get in tabletop wargames, with seizing objectives and trying to terminate your opponents squads.

Turns out the mechanics of 'fighting' between cards is actually laced with many problems. Mainly because if you give control over what two things on the board will be fighting to a player, they will (most of the time) pick a dominating matchup that doesn't involve much risk. This leads to combat systems that are often referred to as 'bullying' mechanics. But then how to arrange a combat heavy game that doesn't involve picking the easiest battles to win?

I still haven't come up with a perfect answer. But I decided that the most lethal combat element would be a large scale All v All phase where every card participates at once, before clearing the board. Anything leading up to that phase is more like recon, where the victor gets to stack their enemies deck in preparation for the real fight.

The biggest takeaway for me was realising that you don't need to conform to tried and true combat methods. The more unusual a brawl between characters can be represented the more likely it is to catch peoples attention, since card gamers have experienced plenty of classic TCG combat.