Diluvian Primordial A very expensive creature with no cost reduction, no tribal support, no flash or anything to keep it flexible, and it allows you to cast one spell from each opponent's graveyard
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The card may see play depending on which graveyard decks are currently most prevalent in the metagame
A card that has been in a certain flavor of green and black decks for quite some time, Hermit Druid provides one of the cheapest and easiest ways to fill your graveyard
One particularly damning thing to note is this chart: This table shows that with 7 Swamp and 7 Plains, you will have the required Plains to cast a turn-3 Territorial Hammerskull only 85.9% of the time (on the play, in absence of mulligans or card selection)