Database: card_games
Question: What is the percentage of the cards with a converted mana cost of 7 in the set Coldsnap?
SQL: SELECT CAST(SUM(CASE WHEN T1.convertedManaCost = 7 THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(T1.id) FROM cards AS T1 INNER JOIN sets AS T2 ON T2.code = T1.setCode WHERE T2.name = 'Coldsnap'