[I copied, deleted, repasted and then edited my previous post, because it was half-baked and the full combo doesn't actually work like I had originally posted (you can't just Power Crush continuously from the 2nd turn on. It takes a bit more set up). That comment above this talking about how the fellow who posted it wishes Latias ex d and Latios ex d were the secret deck seems bizarre without my original post above it to give it context, by the way... you'd think the individual who posted it was a mind reader!]
Okay, forget my original theory, except for the part about Japan possibly winning Worlds and taking it back to their turf instead of Orlando next year. Here is my new theory.
The sixth one is both a reference to this year's Worlds AND a Pokemon, which is Blaziken. Nemes brought this to my attention by pointing out that Infernape is number 6 in the DP Pokedex. Well, all of the "big starting fire Pokemon" from Red and Blue to now end up number 6 in the Pokedex for their respective game/region, including Blaziken. The one I'm talking about is the "resurrected" Firestarter one from Power Keepers. Remember Worlds 2004? Blaziken was having its reign of terror and triumph then. I'm not sure if it won because I wasn't there, but I have a feeling it did. The firedrake is Latias ex d. It's a fire, it's dragon, and it combos with Blaziken and another card I'll get to in a minute. The bastet, as many have said, is Delcatty.
The other combo card not mentioned in the riddle is Latios ex d, because it gives free retreat to the Latias ex d. That is important. Here is the full combo. Optimally, you'll open with Latias ex d or Latios ex d(the latter works as long as you have a Latias ex d in your hand/on your bench, because of its Power-granted free retreat). Latias ex d's Power, Fellow Boost, lets you play 2 energies on it, setting you up for a second turn 90 (when you drop that 3rd energy). The attack, Power Crush, states that if you KO their active, you must discard 2 of those energy. Big set back, right? No, not with Blaziken. Ideally, you'd want your bench to consist of at least Blaziken, one Latias ex d, one Latios ex d, and one Delcatty. The turn after you lose those 2 fire, you're not going to be able to use Power Crush again unless you manage to get 2 Blaziken out. However, as soon as you get two Latias ex d out along with one Blaziken, and as soon as you get 1 fire energy on each Latias ex d (this is crucial), you can use Power Crush every turn. All you do is Firestarter one of the discarded energies back onto the benched Latias ex d, retreat the active one for free via Latios ex d's Power, bring out the benched one (which should have one fire already on it due to a previous energy attachment, and one from Firestarter), attach the third energy to it, and voila. Next turn, you just rinse, lather, and repeat. Delcatty helps you draw and set up, plus it can feed Firestarter. It might seem hard to get all those cards out, since the combo is so intricate, but Holon Mentor and some Celio's plus Delcatty should make it pretty simple (Mentor for the Latios ex d, the Latias ex d, and the Torchic, for example-- assuming you opened with Latias ex d-- and then just focus on getting Blaziken out). Also, Latios ex d's water type and anti-ex attack, plus its low water energy requirements, means a few Rainbow or water energy could be teched in so that you could have the option of putting big dents in fire types AND shut down ex-based decks such as Banette ex.
Even if this doesn't pertain to the riddle at all, I still think it is an amazing and fun combo and I plan on experimenting with it.