Many of these cards, including Field of the Dead and Zombie Apocalypse, are likely meant to show off the effects of the Deadites that were capable of possessing the dead
It also serves as the focal point for many combos, including this rather infuriating one featuring Glacial ChasmGlacial Chasm that prevents all damage that would be dealt to you until the combo can be disrupted
While its Gouge attack can only deal 20 damage at most, Dark Espeons true danger is in its Psysplash attack, which damages each of an opponents Pokmon with a damage counter for every energy card they have attached
The fact that the rarities are fixed makes them balanced for Limited play, while other boosters (set boosters, collector boosters) arent
Removing creatures also clears the way of blockers, allowing our 5-power Commander to swing in for damage whenever able