Frosthaven is one of the best board games on the market. It served as a follow up to the immensely popular Gloomhaven board game, and is one of the most imposing dungeon-delving board games you can buy. It's also really quite expensive.It's not often that we see any sort of discount on this game, but Amazon currently has a Lightning Deal running that drops it down to its lowest price ever. For a limited time (or while stock lasts), you…