Slightly complicated idea, might work better as an event:
Cards are grouped into 6 categories based on popularity, commonality, use, and strategical value. E.G. Graboid is in the 1st category (most useful) while Antlion is in the 6th (least useful). Special: Relic is worth 10 points. Using a card in the nth category gives n points if you win. If you win, you gain the average of the point values of your cards. BO3. Higher score wins (so you can potentially go 1-2 and win). Scores carry over, so you could potentially go 0-3 and win a match.