Shadowverse: Rise of Bahamut

In Star Crusade, they initially promised to introduce a card trading system, but it never materialized. Instead, they added another interesting feature: the ability to purchase weekly cards for credits (similar to rupees). Each week, you could get one random rare, epic, and paragon (legendary) card for a decent, but manageable price. If it weren't for the poor online experience (sometimes taking 5 minutes or longer to find an opponent) and the strange interface changes, I might still be playing.