Ability to permanently see opponent's hand
Ability to add hp to either player (can add negative hp to cause damage)
Ability to add stats to any creature
Ability to add quanta of whatever type to either player (negative quanta removes quanta)
Ability to create certain card in either player's hands
Ability to create any card onto either field
Ability to force either player to draw
Ability to force either player to discard
Doing this would allow for much easier and better playtesting, especially for prospective card designers who want to mimic a card idea's usages.
