Please list the name of the cards in the set Coldsnap with the highest converted mana cost.
card set Coldsnap refers to name = 'Coldsnap'
SELECT T1.name FROM cards AS T1 INNER JOIN sets AS T2 ON T2.code = T1.setCode WHERE T2.name = 'Coldsnap' ORDER BY T1.convertedManaCost DESC LIMIT 1