Energy acceleration, the ability to attach more than one Energy card per turn or attach Energy from places other than your hand, is a cornerstone of many powerful competitive decks
Mai, Scornful Striker Mai, Scornful Striker excels at punishing opponents
In the age where Shadow Games were used to determine a person's fate, the Priests used the Millennium Items and sorcery to pull out and seal the souls (Ka) of criminals, which take the form of Monsters Spirits, into stone slabs to do battle
Not only does it put a lid on teamwork, I often got stuck having to play bad actions from bad cards, doing something completely against what I actually wanted or needed to do, and thats about as far from fun as I can imagine in a cooperative board game
Cloud's Limit Break can act as both single-target and mass creature removal depending on the mode you choose