Symmetric effects

Symmetric effects are effects that impacts all players the same way. Both positive and negative effects can be made symmetrical, and typically that means the effect could be made cheaper than if it only affected one player. The strategic downside is often two-fold: firstly, the caster invested mana into a spell, while the opponent did not. Related to the first, that means the opponent typically has a greater chance to exploit the symmetry as they would get to have their next turn unhampered by having tapped mana to cast the symmetrical card.

Some of the most powerful cards in Magic feature symmetric effects. A proper understanding of symmetric effects will give you an advantage in both deckbuilding and gameplay. Critically, the player casting the spell should understand their reason for casting it and have a way to break the symmetry, taking advantage of the discount afforded. Mind Rake is a very clear demonstration: a Mind Rot is fine if unexciting at three mana but casting it for two mana means the caster suffers equally, and in most cases suffers more as they invested mana into the situation. However, if the caster has one or zero cards in their hand after casting Mind Rake, the opponent loses more cards in the abstract, and the mana discount would have helped in casting spells faster.

Board sweepers like Wrath of God are the most classically exploitable symmetric effect. Destroying all creatures can be exploited if one plays only creatures that are indestructible or can regenerate, but most often the exploit is having no creature or relevant creature in the deck to start with, bringing forward the classic gameplay of the control against aggro matchup.

In the inverse, a card like Eidolon of the Great Revel typically does not live in a deck where the mana values of all the cards are above 3 to avoid the damage tax; rather, the player with the Eidolon plays it later and uses cheap spells to pressure the life total, as the ultimate symmetry here is that no player can play more than ten cheap spells after it is cast, but the ten is reduced by each two damage taken beforehand. Because the symmetric condition is so broad, it affords the caster the ability to attack the axis on which the symmetry is focused before it becomes relevant.

Broader metagame strategy can also influence this. Veteran Explorer of the Legacy Nic Fit deck should by all rights be something difficult to exploit because all decks use lands, but the context of Legacy is that even if basic lands were sufficiently played, the format's decks did not run spells that cost four and rarely run spells that cast three, and so the deckbuilding to take advantage of that by using high impact spells that would normally be too slow to cast, and while the opponent's tempo may be increased by the same lands, their power would be dampened by the specific threats chosen for Nic Fit. However, increased power level in newer sets made expensive spells more favorable, weakening this archetype.

Timetwister and Memory Jar were famed for their opaque but easily breakable symmetry, giving the former the honor of being in the Power Nine and the latter being emergency banned.