The cynical take writes itself: game developers are exploiting nostalgia, hooking minors on what Iona calls legalized gambling for kids, and manufacturing scarcity to juice profits
Being able to play Riteknife in some sort of Grixis nastiness deck or a Mardu aggro deck with the knife in the hands of anything from a Mirran Crusader to a Grateful Apparition means you only have to sac one creature to get the Riteknife party started because Proliferate will take care of the rest
Thrummingbird Thrummingbird is the Phyrexian bird horror that could, giving counter-based decks a consistent source of proliferation since Scars of Mirrodin
Of course, this only makes the fact that Snapcaster Mage isnt the featured bonus card that much more painful
to be honest, while were still not 100% sure why its all necessary, we can live with it
It's basically a Basic form of Wigglytuff, with 10 more HP AND deals 10 extra damage