These events require little to no cards to participate, and you get to open new packs and build decks on the spot
Here are links to some of those previews, along with an official video
They can also block attacking creatures, absorbing incoming damage
Commanders like Feldon of the Third Path can make good use of it, for example, or it can pay for the vast majority of Herigast, Erupting Nullkites emerge cost
Worldknit Having no sideboard in a Limited setting can be restricting because adapting to your opponents decks is important
The support cards so far either aid on using those effects, such as "Graydle Parasite" and "Graydle Impact", or help swarming "Graydle" monsters, such as "Graydle Split"