The 魔力再生药水 is a 增益药水 which grants the 魔力再生 增益 when consumed. The buff increases the rate at which the player's 魔力 regenerates. The buff lasts for 7 minutes, but can be canceled at any time by right-clicking the icon.
The natural rate of regeneration is modified by whether or not the player is moving, and how much current mana a character has. This formula exists to punish reckless mana use - spend all your mana, and you will not have any recovery until you stop moving or use a potion. Conversely, when the player waits between uses of magical weapons until mana is refilled, and stands still, mana recovers at its fastest possible rate.
This potion acts as if the player had more current mana than they actually have, meaning that the player regenerates mana as if they had full mana and were standing still, even if they were moving. In addition, it will also greatly reduce the mana regeneration delay(by setting it to a very small number). Hence, using this potion, the player will regenerate mana as quickly as someone specifically trying to regenerate mana quickly even while using mana recklessly. (Making it excellent for Boss-fighting situations, where high mobility is paramount to survival.) However, mana still does not regenerate for a small duration after any magic is expended.