It points out the fact that this will be the new normal for the format because all Universes Beyond prices will be like this moving forward
It shuts down other effects as well - your opponents can't cast spells from anywhere other than their hands, so no casting spells using Madness, Plot, Mayhem, or a whole bunch of red impulse draw effects
It's super cheap but it cannot stop tramplers, and it's on the ground
It's unclear whether this was the most necessary of the Slivers, but it was the one that frustrated the most opposing plans to deal with the problem and even opened up new game plans when the card advantage resulting from saving your creatures could allow Sliver decks to go the control route when backed up by counters and removal spells
When Elsa quests, you can exert a character of your choice, and with Anna in play, that character is also prevented from readying at the start of their next turn
Since August 2024, Wizards of the Coast has said MTG banlists should happen once a year, except in rare, particularly urgent circumstances