In a dedicated Landfall deck, she can decimate foes in a handful of turns, due to how ridiculously high her Power can get, made even more terrifying with her Trample
More notably though, much of Arceus' power is tied to "Link Abilities", passive powers that it triggers in certain other cards from the expansion
But what makes these cards so special
There are currently no purchase limits in place
Once you reach the phase of the game where you can afford to do multiple things per turn, you need card draw to ensure you keep having things to do (Circle of Power, Fight On!, Travel the Overworld) or at least cards which can be used multiple times (flashback spells, Ring of the Lucii, Shambling Cieth, Relentless X-ATM092)
Qliphort had originally fallen off after the banning of Apoqliphort Towers and limiting of Qliphort Scout and Saqlifice