This means that if an opponent wants to play a land, they'll have to ensure that there aren't enough for Impending Disaster to trigger
Because instants can be cast at any point you have priority, theyre great for protecting creatures, killing creatures, or stopping other spells
For many people, it can be a long wait between games with friends
Take the Planechase cards in the March of the Machine precons and the Doctor Who precons, for example
This was often used as discard fodder to things like Psychatog, Wild Mongrel, or Merfolk Looter, then cast from the graveyard for two mana
Currently, the featured listing is a near-mint foil for $798.88