It mainly appeared on black cards with a few exceptions like Hooded Kavu
But you can interact with it just like you could with any other enchantment if its in play, in the graveyard, in someones hand, in a library, etc
You dont really get to read the names of the creatures, but their power and toughness are clearly indicated, and the art is sizable enough to help identify them quickly
You can call it canon at any time because thats what the multiverse implies, but at the same time those promotional cards were just card styles and not actual standalone cards like the Street Fighter or Walking Dead Secret Lairs
Even if you don't have counter magic good players will not make critical plays into you if they can avoid it
I only wish I could have picked a Magic card that would have you flip a coin as part of one of its abilities