Shadowverse

Haha, I just played a game where I was constantly attacking the Forest faction's portal. I meticulously cleared his side of the board every turn, saying, "I can do this all day!", and then he eventually fell to Sapphire. Before that, I played a similar control game with a control Blood faction in an unlimited game. I realized that people find enjoyment in portal strategies.
Although I don't agree that it's a mid-game strategy; to me, it's closer to a control strategy.