Mana

Mana is a resource consumed by the player in order to use magic weapons. The player's current and maximum Mana is shown as a vertical meter of blue stars on the right side of the screen (example is shown above). Mana regenerates automatically as long as the player isn't firing a magic weapon; in addition to filling more quickly if the player stands still, regeneration speed scales based on the player's current mana.

Each character starts with 20 maximum mana. Using Mana Crystals increases the player's maximum mana by 20 permanently by adding another star to the meter, up to a maximum of 200 (Gaining 9 Mana Crystals, 10 stars on the side all together). The last star on the mana bar makes a pulsing motion to make it more easily visible.

Mana can be increased further through the use of various accessories and armor.

Affecting Mana
In order to use magic weapons more often, certain items can increase the maximum mana or reduce the cost of using magic weapons. Because of how mana regeneration works, these can also effectively increase the rate of mana regeneration, so long as the player takes care to stay above certain current mana thresholds.

Restoring Mana
Mana regenerates on its own when not in use, until the player's current maximum is reached.

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 have almost no regeneration at all until you stop moving or use a potion. Conversely, when the player stands still waiting between uses of magical weapons until mana is refilled, mana recovers at its fastest possible rate. Wearing items that increase the maximum mana can thus also increase your rate of recovery, as each use of magic will still leave you with more remaining mana, and the higher multiplier.

Standing still apparently multiplies the rate at which mana regenerates, by roughly twice as much.

However, mana does not regenerate for a small period of time after any magic is expended, meaning that in order to start regenerating mana the player must stop casting spells for a short time. The regen cooldown starts the moment you stop spending mana, so casting Magic Missile and Flamelash will start the cooldown as soon as it is cast, regardless of how long the projectile is held. Setting up Star Statues on Timers can help give magic-using players much better rates of magical fire in boss-fighting or enemy-farming situations where you have the time to prepare where you are going to fight. (A Crystal Ball is also helpful in such situations.)

To be more specific, the mana regeneration has a similar mechanism of health regeneration, there is also a mana counter, which is increased by a mana regeneration rate every tick. When it reaches 120 or more, it would be reduced by 120 and increase mana by 1. (So, 1 mana regeneration rate equals to 0.5 mana per second)

Also, there is a mana regeneration delay, which would be set to a certain number calculated by the formula below (round up after the calculation), if player used any Magic Weapons: mana regeneration delay = 0.7*((1-current mana/maximum mana)*240+45) And it will be reduced by 1 (if moving) or 2 (if standing still) every tick (also an additional 1 per tick if wearing the Mana Regeneration Band). Once it reaches 0, the mana regeneration rate would be calculated by the formula below:

If player is moving: mana regeneration rate = (maximum mana/7+1+bonus)*(current mana/maximum mana*0.8+0.2)*1.15 If player is standing still: mana regeneration rate = (maximum mana/7+1+maximum mana/2+bonus)*(current mana/maximum mana*0.8+0.2)*1.15 (note: in both formula, the bonus will be 0 normally, and would be 25 if wearing the Mana Regeneration Band).

Then, if player is have the Mana Regeneration buff the mana regeneration delay will be reset to 20 if it's more than 20, and it would always treat the player as standing still and having maximum mana. So, it would act like this formula: mana regeneration rate = (maximum mana/7+1+maximum mana/2+bonus)*1.15

If a player wants to rely on magical weapons for normal exploration, they should memorize how to best recover mana, even while distracted. To make the most of mana regeneration, the player should practice understanding the timing between when they fire, and when the tone that indicates they have recovered full mana occurs, (so that they fire their next attack at exactly that moment,) and try to remain stationary during times when the mana recovery starts. Firing can be practiced in a safe location like the player's home until they are comfortable with how their regenerate their mana.

There are also several items that can be used to regenerate mana:

History
Mana Mana