The serialized Headliner of the set is The Aetherspark, which is also pretty desirable in its other prints
The intent is for the Mastery Track to get the same amount of rewards as the weekly reward system was paying out, in addition, the Set Mastery Orbs has been added on top of this
You may want to flash it out to surprise chump something or to swing on a tapped board by casting at the end of that players turn
Abyss Eye is especially exciting as it introduces newer Mega Evolutions inspired by the Mega Dimension DLC, including the fearsome Mega Darkrai ex
Strength of the Harvest/ Haven of the Harvest I had to reread Strength of the Harvest to realize this counts enchantments and creatures, not artifacts
The actions you can take are: Playing a Pokmon to your bench (as many as you like, up to 5 total benched Pokmon) Evolving your Pokmon (you can evolve each Pokmon once per turn, and not on the turn they were played onto the board) Retreating your Pokmon and promoting a benched Pokmon to the active spot Attaching an energy card to your Pokmon (once per turn) Playing a trainer card (you can play as many items, stadiums, and Pokmon tools as you like, but only one supporter per turn) Using the stadium in play (once per turn) Using Pokmon abilities (once per Pokmon per turn) Attacking your opponent's Pokmon Keep in mind that occasionally, a card will affect these actions and make them either impossible or more frequent