The Lugia found in the Aquapolis set is not only the rarest and most expensive hit in the set, but it is also one of the most expensive Pokemon cards ever printed before you start looking at the graded market
1 Red-Eyes Dark Dragoon "Red-Eyes Dark Dragoon" is a meta-warping card that is played in every single deck, "Red-Eyes" or otherwise
With reprints being more common in English than Japanese, the value of rare cards drops sharply when reissued
Finally, the fact that the creature Self-Destruct targets actually sees it resolving is a big deal in current Standard
It's a matchup normally decided by skill, because it's important to get to your Fusion as fast as possible by sending it qith Squamata a lot of the time, and it's also important to try and not leave Fusions out - Beast is good for this as you can Tribute Summon
Koraidon ex and Miraidon ex are also confirmed to be part of the set list