You can order one of them for yourself and keep all the decks or share the cost with friends and get into a match right away
Aura Shards is already a marmite card, but putting it on a creature and offering other useful modes alongside it makes for a tempting inclusion for many decks
It's an enchant creature card
In super rare cases, a card is cut while folded, leaving a little bit of extra cardboard attached to the card (aka a flag)
The most direct way is cards like Knights of the Black Rose
Aether Revolt was overshadowed by the day-one errata for Felidar Sovereign and the ban for Smugglers Copter and Emrakul, the Promised End, Ixalan was bizarrely underpowered, and the supplementary sets were wearing thin, with Iconic Masters a particularly discouraging fizzle in the Masters line