Also known as Gigantamaxing (or Eternamaxing, which only affects the Legendary Pokemon Eternatus), Dynamaxing was brought into the Pokemon Trading Card Game (TCG) with the arrival of VMAX Pokemon
Power Hourglass Tool At the end of your turn, if the Pokmon this card is attached to is in the Active Spot, you may attach 1 Basic Energy card from your discard pile to that Pokmon
Mewtwo - Psychic - 130 HP Pokmon - Basic CC Reflective Barrier 20 During your opponent's next turn, if this Pokmon is damaged by an attack (even if it is Knocked Out), put damage counters on the Attacking Pokmon equal to the damage done to this Pokmon
Not only that, but the Creature gains Indestructible until end of turn whenever you cast a spell, making combat a nightmare for your opponent if you have open mana
Im not and have never been an MTG judge, but you can sit back and enjoy this summary of how to use the level up mechanic (insert Super Mushroom sound)