Making interesting decisions for your opponent means giving them hard choices about what they want to give up (yes, good discard means making your opponent suffer you're playing black after all)
In past Un-sets, silver-bordered cards have featured unique keywords such as Art Menace, Super Haste, and Gotcha
Even one successful use is generally worth it, and if you have the means to shuffle your library through a fetchland like Misty Rainforest, a tutor effect like Worldly Tutor, or even another mana ramp spell like Skyshroud Claim, you can improve your odds of success dramatically
Players may turn face-down creatures face up while a spell with split second is on the stack
All of the new cards will be spells, lands, and creatures set on Ikoria, while any reprints could potentially be from anywhere within Magics pantheon