In the heat of battle what is needed is a good fog to cover the land. In Magic: the Gathering Fog does just that is dissipates the war of combat and give the player a reprieve until next turn. Like Lighting Bolt, Fog can provide a number of advantages to players.
At its core, Fog (G), “Prevent all combat damage that would be dealt this turn” acts as a relief to players who might be in a tight spot and allow them to prepare for their next turn. When played in TurboFog type decks it is used frequently putting the opponent at a disadvantage when attacking. Allowing the player to Fog then next turn all-out attack. It allows the player to dictate the outcome combat.
It is the design as an instant rather than a sorcery that helps make Fog so potent. Knowing that an opponent can have an army of creatures only to be stopped dead in their tracks by one spell.
But there are other cards like Fog that are arguably better. Tangle is one such card. Tangle (1G), “Prevent all combat damage that would be dealt this turn. Each attacking creature doesn’t untap during its controller’s next untap step,” has an added ability that give it a little more kick. Though Offset by its casting Cost (1G) compared to Fog (G) it puts the player at a bit more of a disadvantage. When looking at the opponents field, if they outnumber the player Tangle literally tangles the creatures for a turn and give the player almost free game to swing out next turn.
Now these Prevent Damage cards are great for when there is an army at your door step, but because of their design they still leave room for indirect combat damage. It is because of cards like Fog Tangle and even Heavy Fog that allow players to match wits with fast aggressive decks.
When building decks it does not hurt to think about the state of the battlefield. Understanding how the field might look can help a player determine their plays and how they want the match to flow when utilizing cards like these.