Relentless Rats est la toute première carte imprimée mentionnant explicitement dans son texte que son nombre d'exemplaires n'est pas limité dans un deck. Elle s'inspire de la carte
Plague Rats, qui, d'après une légende urbaine de Magic (voir
cette anecdote), aurait été jouée à l'origine dans des decks en contenant un nombre non limité à 4 exemplaires.
Elle sera suivie ensuite par
Shadowborn Apostle,
Rat Colony,
Persistent Petitioners,
Dragon's Approach,
Slime Against Humanity,
Templar Knight et
Hare Apparent.
La carte
Seven Dwarves (respectivement
Nazgûl) présente quant à elle une variante, puisque son nombre d'exemplaires n'est pas illimité, mais limité à 7 (respectivement 9) au lieu de 4, en cohérence avec son
flavor (voir
cette anecdote).
Search ~ Texte : "A deck can have"
R&D tried numerous times to recapture the feel of Plague Rats, usually choosing to make the creatures bigger based on all your Rats.
Then during Fifth Dawn, we tried a new approach. What if the card just let you include as many copies as you wanted to play? [...] Once we had the "a deck may have any number" technology, we used it, although sparingly, on other cards. In the beginning, it was just used in black, although not always on Rats.
Ravnica Allegiance introduced the ability to blue, and Throne of Eldraine and Strixhaven would give it to red. The Council of Colors have talked about this. We've determined that, as long as the card fits into its color, any color can have access to "a deck may have any number" text.
In Throne of Eldraine, I wanted to capture the flavor of the seven dwarves. My original plan was to have exactly seven Dwarf cards in the set, but it took up too much space and was a little too much of a constraint on card concepting. My solution was to make one card called Seven Dwarves and then make a variant of the Relentless Rats template. Instead of letting you have any number, the card lets you have up to a specific number. In this case, seven.
We used that technology again in The Lord of the Rings: Tales of Middle-earth. We knew we wanted to have Nazgûl. They're one of the big villains in the story, but like the seven dwarves, we didn't have space to do nine. Luckily, we'd solved the problem already. Nazgûl uses the Seven Dwarves technology and becomes the first card where you can have up to nine copies in your deck.