Earthen Vessel is among the most prominent items in the Pokmon Trading Card Game, because every strategy needs a way to ensure that they find energy so their Pokmon can attack
Gameplay-wise, Altered features two combat lanes (called Expeditions), each led by a Hero, and uses a flexible resource system where cards can be used as energy, kind of like what you see in Lorcana or Pokmon
The Basic Grass Energy card powers Grass-type attacks
A report from Pokebeach indicates that demand for Prismatic Evolutions will outweigh the supply of the set
Investors who are keeping old stock, and even some modern, for quite some time are preserving the state of the TCG at that very point, but without collectors interested in those products, what would be the point
This type of effects can either be a way to balance the power of your Pokmon or part of some mechanic aimed to make them more effective (for example increasing the damage of their next moves)