Mass removal is a somewhat nebulous term, usually interpreted as “board wipes”, or cards that completely clear the board and reset it to an earlier state. I choose to describe mass removal spells as spells that answer multiple threats without help. In slower decks, these invalidate the early aggression of opponents and allow your bigger spells to take over. In faster decks, these can prevent opponents from outclassing your smaller threats as the game goes long. If built into the deck’s strategy, these can act as win conditions. If just thrown in, however, these can stall the game and frustrate the table.
Unlike Universal Mass Removal, which requires building around to generate an advantage, One-Sided Mass Removal is designed to set everyone else back, but keep the caster ahead. This can either create the advantage needed to win the game, or seal a game one is already winning. In short, if you want to win more, these are the cards that will help you do it.
Limited Scope
Mass Removal that is limited in scope is a great way for decks that don’t use a color, permanent type, or zone to affect others while leaving their own board untouched. Wash Out is a way to hit a color you’re not playing really hard; Creeping Corrosion is a solid anti-artifact card for green decks that don’t use a lot of them; and many decks that don’t use the graveyard love spells like Tormod’s Crypt or Relic of Progenitus!
Multiple Targets
Most Mass Removal is powerful because of the lack of targeting, the same way that exile is typically preferable to destruction: both reduce the amount of counterplay. There are, however, plenty of powerful spells that can be considered mass removal because of the fact that they have multiple targets, like Decimate, Hex and Aether Gale. These remove just the permanents you want, keeping the game from being totally reset.
Pyroclasms
Pyroclasm and Infest effects kill or shrink small creatures or particular creatures, like Earthquakes or Hurricanes. These scaling effects enable you to wipe the board of just what you want dead. The ability to control the damage is key to breaking parity and shifting from defense to offense.