That scarcity has driven this card to huge new heights
We can also use Wrenn and Seven or Nissa, Vital Force to return permanents from our graveyard to our hand, which can lead to some really weird legend-rule loops where we play multiple Ugin, the Spirit Dragons or Nissa, Who Shakes the Worlds, use their abilities, with each copy legend-ruling away the first, return them all to our hand with Wrenn and Seven, and eventually kill our opponent with Ugin damage or a massive Nissa, Who Shakes the World land (which gets especially massive thanks to the extra counters from Doubling Season)
Establish a handful of elves or faeries and the more you control, the more spells you can play from among your opponent's cards
While Witherbloom and Prismari feel like the top two in terms of raw power, the other three Elder Dragons still have plenty to offer
With proper sacrifice outlets, you can even remove their creatures entirely for your own benefit