A variety of creature-toolbox decks rely on Chord of Calling as an instant-speed tutor to find silver bullet answers like Reclamation Sage and Collector Ouphe to hamper their opponents, or to assemble value engines with cards like Yawgmoth, Thran Physician
Thanks to the way poison works, Blightsteel is a one-hit kill if it's not blocked, but throwing creatures in front of this beast will see them killed or shrunken, and you'll likely still take some poison damage
there has to be counters that balance them out
These releases demonstrated that the value of a card was determined not solely by the uniqueness of its specific printing, but also by its gameplay value
And this doesnt mean necessarily winning through damage, but rather playing so many spells that it becomes a consistent threat thanks to it giving prowess to your other creatures, while also being able to use both your and your opponents spells from the graveyard