The low cost and deployability definitely point to being an Eerie generator, which makes its very simple effects even more universal if you decide to put this into such a dedicated deck
25th Anniversary Rarity Collection II packs have twice as many Ultra & Secret Rares per pack, which gives you twice as many chances at luxury rares per pack (Quarter Century Secret Rares, Prismatic-style Ultimate & Collectors Rares, and Platinum Secret Rares)
The battle at the big bridge offers a nice instant effect, as does Galuf's final act
Cards that are easy to access, work in multiple decks, and remain effective regardless of game state tend to dominate competitive play
The front side can take a while to transform but with Scry or some other library manipulation, the trigger can happen quickly
#7 Have you considered changing elves to insects