These Mega Ultra Rare cards feature unique artwork not found anywhere else, and are different than the hyper rare cards of the past
Damage counters represent the amount of HP lost up to that point, so this attack will do between 20 damage (if Steelix is at full health) and a frankly outrageous 360 damage if it's down to 10 HP
Again, you should immerse yourself in the community: watch videos, follow forums, ask around, and maybe even get into the game yourself so youll have a rough idea of what a card should be worth
Warping in and attacking with an Overlord of the Boilerbilges for three mana seems great
Timing is another important consideration
The artwork and effect make it a standout among DBSCG extra cards, especially for blue-based decks