Trying to finish the quest with the Life Splinter proved to be hard today. I've tried to boost a bit my cards and I bought ~20 of them and combined them with my existing in order to get them to the Level 4. That kinda helped... well, not really. I still kept losing to the guys with L4 & L5 cards.
The break came when I played against a guy using the Fire cards at Level 1. Gold III is but a dream now.
