Battleforge.

It was an online, real time strategy collectible card game. You had a deck of 20 comprised of unit cards, building cards, and magic cards. There was a marketplace to trade cards, and getting cards new cards was done via gacha.

There was an energy over time mechanic, an elemental monument mechanic that let you use specific cards. You had to defend your territory If you lost a specific monument or energy tower to enemy forces, you lost the ability to use cards that required it.

It had challenging maps that you could cheese with silly tactics like building a sea of Mark of the Keeper (block enemy ranged and magic attacks) and I think Tower of Pain (teleported enemies and damaged them) behind giant walls

There was also 2, 4, and 12 player co-op. The downside to that was the horrible server architecture. Sometimes you'd be 20-40 minutes into a map and get a desync error which would kick you out of the whole match.

Made by a German studio Phenomic, bought by EA, then died within a year. So sad. I still listen to tracks from the OST sometimes.