Temporal Echo

You send a probing echo of yourself into the future but moving through time in reverse. Pick a location you hope to be in a minute or less. The DM decides whether it is at all possible for you to physically get to such a location using your natural walk/climb/fly speeds in an minute or less from your current location. This consideration should include inanimate physical obstruction (e.g. a locked door, a lake) but not animate obstructions that would have to actively inhibit your travel (e.g. a monster). In other words, if time were to freeze for every other entity for a minute, would you be able to reach this destination? If no, the spell fails to cast, but you know that the destination is currently unreachable in that time. If yes, the echo manifests at the chosen location. 

The echo manifests as a transparent image of yourself but doing everything in reverse (i.e. walking backwards). The echo has your stats and conditions at the time you cast the spell, but none of your equipment. In combat, it has the same initiative as you and acts immediately after you. When it first manifests, it is unconscious on the floor of the chosen location, has 1 HP, and has expended all its spell slots.

For the duration of the effect, whenever you take damage, the echo heals for half that amount, and whenever you cast a spell, a spell slot of 1 level lower is restored for the echo. 

The echo moves towards you unwaveringly. Every turn in combat it moves the maximum distance it can on the trajectory that will bring it to your current location most expediently, and it takes the dodge action. The echo is immune to physical forms of damage and resistant to all others. 

When the echo reaches you and touches you, it merges with you. Your current HP is replaced with its current HP at the time of touching you, your open spell slots are replaced with its open spell slots, and any conditions you are experiencing are replaced with its conditions. In addition, you become aware of everything the echo experienced on its journey towards you. 

The spell ends and the echo disappears if you die, the echo returns to 0 hp, the echo merges with you, or if the duration of the spell is elapsed.