If a spell is cast as an Adventure, its controller exiles it instead of putting it into its owner's graveyard as it resolves
The first one is Oko, the Ringleader, as one might expect
If I'm off, comment and let me know
For most intents and purposes, it is a Watchwolf (an appropriately-positioned beatdown deck can play one on turn two and in theory be very happy with the return), but here you get some bonus synergies
Suddenly, you can go for it without worrying about the Force of Wills your opponents might be holding
It used to just be Commander sets, but now we have Universes Beyond, Secret Lairs, direct to Modern sets, and now a player who started in the last year and only purchased newly released products likely cant play most of their collection in Standard