Regardless of what happens in the Pokemon market, this card will always command a high price.
The slower the deck, the harder it is to accommodate Leyline
A 4/4 for five mana is a good rate when it has other abilities, even in these days of more powerful creatures
The mid game and late game are all about survival, accumulating permanents with triggered mill abilities like Ruin Crab and Memory Erosion, play instants and sorceries that mill some more like Mind Grind, and play spells that benefit greatly from the resulting increase in graveyards like Guiltfeeder and Avatar of Woe
Since you'll need several creatures in your graveyard to use Mimeoplasm, Revered One effectively, there's a graveyard theme that includes mill effects and reanimation , including a couple ways to play lands from your graveyard
(2020-08-07) If you gain an amount of life for each of something, that life is gained as one event and the ability triggers only once