So if youve got a board full of cheap artifacts, enchantments, and creatures (even tokens) with just a single strong non-legendary creature, suddenly they all become that same creature
How useful bulk will be for you depends on what type of player you are and the reason for your purchase
The eight MTG card types are: Sorceries Instants Lands Creatures Artifacts Enchantments Planeswalkers Battles Sorceries Sorceries (and also Instants) represent magical effects you can cast, like a fireball or a summoning spell
The choice of which cards appear more frequently on the sheets appears more or less random (non-holo Flareon is more common than non-holo Jolteon and Vaporeon, for example)
This power can't be used if Entei is already Asleep, Confused, or Paralyzed when it is damaged
I could go on about why these creatures are good in affinity but with the majority having been constructed staples in the deck I am sure there is more than enough literature out there already on why they are good