But at least from a competitive standpoint, there wont be another period of time where easily accessible cards will be viable in matches like the launch of a new game
During an early press preview, WotC showed off some of the Partner Source Material Cards: Eladamri's Call, Heroic Intervention, Mystic Remora, Dark Depths, and the $45 Cruel Tutor
Any effects that interact with counters a player gets, has, or loses can interact with energy counters
you can run Forbidden Knowledge and/or David Renfield and have a satisfying source of resource generation, but the best part of this card is that it can give you a certain amount of resources and/or cards, what you need at most at the time you use it
For example, Abomasnows attack requires one less energy while Arceus or Arceus EX is in play thanks to its Vigor Link ability
Whenever Omanth, Locus of Rage or another Elemental you control dies, Omnath deals 3 damage to any target