Card condition may be indicated by HP, MP, LP, and NM. These mean heavily-played, moderately-played, lightly-played, and near-mint. Condition is a huge price factor, and you can find a guide here
the Maenads, a group of nymphs who follow Dionysus, are a classic example
With infinite mana, you can go through your entire deck this way until you find a way to win
Even if Vogar does die, cards like Supernatural Stamina and Gravewaker can bring it back to play.
Like most Pokmon cards, the value of Mewtwo LV.X depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Legends Awakened)
However, its three notable chase cards that buoy this sets booster boxes to the lofty heights its market price reaches: Mox Diamond at close to $600, the first legendary Sliver creature, Sliver Queen, at $250 and recursion engine/nonbasic land Volraths Stronghold at over $80