In Ruldo Forest, go to where Gurd was standing and walk through two trees there you will face three Cocktraces. Defeat them to have access to the battle arena in the mountains. There you must defeat all guardians(if you cannot go in, improve your skill level with that element until it has six stars) and collect there cards to unlock the second arena. Raise your ability with the Neutral element to six stars and go through the door. You will face a really strong creature that guards the next door. Defeat it and proceed. In that door, you must defeat Helena. Her stratigy and cards are very similar to the one she used in the first Lost Kingdoms. If you are victorious, you will recieve an Ice Skeleton card and you can now choose Helena as one of your characters in Vs Mode.