Update (8:00 PM): Added exciting new info and made a few points clearer.

We have just learned some exciting LEGEND: HeartGold and SoulSilver news concerning new game mechanics and set info thanks to our longtime contact in Japan, Kareda. The news is as follows…

• The EX / LV.X of the “LEGEND” era will be called “Great Pokemon.” They are Pokemon that “specialize in battling.” There will be eight of them in the set. Their names will be in holofoil.
• A new game mechanic will be placing two individual Legendary Pokemon cards together to form an even stronger card with better attacks and HP. Ho-Oh and Lugia are confirmed to be combinable in this manner. We are not too sure how this will work yet. The cards may be named “Lugia LEGEND” and “Ho-Oh LEGEND” in reference to the set block’s title (speculation).
• As we reported previously, the set consists of two mini-sets which will be combined to form our English set. There are 70 cards in each of the two mini-sets.
• One secret card per set.
• No overlap between the two sets, except for eight basic Energy cards.
• The sets will feature redesigned basic Energy cards. Each Energy type will also apparently feature silhouettes of certain Pokemon. We’re not exactly sure how this will turn out - collectible Energy?
• Each booster pack contains 11 cards, two of which are holo (one regular holo and one holo Energy card).
• The Random Basic Pack sold along the release of the set has 60 cards. 30 are random cards from the mini-sets, and six of those are holos. The other 30 cards are basic Energy (not the redesigned ones). The pack also comes with a bonus Red Gyarados card not from the sets.
• Using the miracle of math, our English set should have 135 cards (71-8, x2, +1, +8).