In the video game Dark Souls, a key strategy is to watch for an enemy to start making an attack, such as a melee attack or breath weapon, whereupon you tumble out of the way to avoid the attack. The attack strikes your previous location, and you are unharmed.
Is it possible, within the standard rules of D&D 5th edition, to ready an action to avoid an attack or special attack (e.g. breath weapon) in this manner?
While it is not a readied action, the point is that you anticipate attacks and focus on getting out of the way. It gives Disadvantage to any attacker you can see and gives you Advantage on dexterity saving throws (e.g. against certain breath weapons). The rules are on page 192 of the PHB.
The text says (emphasis mine):
"To do so, you can take the Ready action on your turn so that you can act later in the round using your reaction…[w]hen the trigger occurs, you can either take your reaction right after the trigger finishes or ignore the trigger" (PH193).
So you can actually ready such an action but it will occur after you would take the damage you are trying to avoid.
As Szega stated, you would likely be better off using the Dodge action instead.
When you take the Dodge action, you focus entirely on avoiding attacks. Until the start of your next turn, any attack roll made against you has disadvantage if you can see the attacker, and you make Dexterity saving throws with advantage. You lose this benefit if you are incapacitated or if your speed drops to 0.
