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.
Fogs
Fogs might not feel like Mass Removal because they don’t really remove anything from the board. The game pieces that were out are still out, and continue to pose the same threat in future turns. For the current turn, however, they do not deal damage, and, if they tapped to attack, they stay tapped and are unavailable to block, allowing you to attack them back!
Mass Protection
Mass Protection is an intriguing way of looking at Mass Removal, as it allows your board to survive what would otherwise have been a Universal Mass Removal effect. As a result, it’s like you used the Mass Removal with a plan to take advantage of it, allowing you to continue as the aggressor, and thwarting the plans of the Universal Mass Removal! In fact, cards that do this, like Teferi’s Protection, can be so gamebreaking, they act as win conditions!
Mass Unblockable
Mass Unblockable effects might not take cardboard off the table (unless you use them to remove a player), but they do invalidate quite a lot of cards. Siege Behemoth, Open into Wonder, and even Falter effects allow your board to bypass your opponents’, no matter how secure they think their defenses are!