Psy Shadow says "take 1 [P] Energy from your Energy Zone" and Inferno Dance says "take an amount of [R] Energy." There's no mention of Energy "cards" like there would be in the real game
For players who enjoy chaining spells for maximum impact, timing your prowess triggers can create moments that feel almost cinematic
The last ability gives you a discount on spells you cast from anywhere other than your hand, including the top of the library
Finally, if you have a large number of Creature cards with the same converted mana cost in your deck, you could make use of the conspiracy Emissary's Ploy to fix your mana and make them easier to cast
I am not advocating that you should go out and buy ten foil Purphoros right away
Among the different decks, each one also comes with a unique playstyle and approach to winning the game, so no two are going to be the same