By discarding an energy card, players can draw two cards, which is great for maintaining hand advantage, but also setting up the discard pile for important plays with cards like Regidrago V and Palkia V
Supporter cards and item cards, for instance, focus purely on things like drawing another two cards, dealing 10 more damage with an attack, switching out opposition Pokmon or reshuffling opponents' hands
Theres no word on what exactly these will be, but its a good bet that these are going to be Ncuti Gatwas incoming The Fifteenth Doctor and his first companion, Ruby Sunday.
Even if Roon isnt your commander, as long as your blink deck has access to blue and/or green plus a blink spell that can target opposing creatures, this can be a nasty little trick that your opponent probably wont see coming the first time, and one theyll have to consider playing around thereafter