A Magipen is a tool in the world of Magience which uses magic power, or mana, to write on anything - even air. It doesn't actually contain any ink and so can never run out but the enchantment that makes it work can wear off over time, making the writing fade until eventually it won't produce anything at all. It does use a miniscule amount of Mana so using one reduces the MP bar, though even the most mana-intensive pens don't draw enough for the user to notice anything even if they don't have much MP to begin with or have been drawing a long time. Most Magipens cost 5 copper.
The color of the markings a magipen can make is set by default to be the user's aura color. They can also be made to have special effects for a minor cost increase, such as glowing, sparkling, or even wiggling around on their own. Magipens that can write in set colors different from the user's aura will cost a bit more, up to 1 silver depending on whether the "ink" has any special effects or not.
The markings are controlled by the user's will, since they're manipulated by mana. If a user concentrates they can make the markings move, creating animations, or erase them if they make any errors. By default a magipen's markings will fade within an hour, though for a higher cost of MP they can be made to stay longer - magipens can also be purchased whose markings will last for quite some time.
The "ink" of a magipen counts as magic and can be dispelled, absorbed, altered, or eaten if someone is capable of eating magic.