I have been thinking about a magic system that is about "e=mc²". Main concept is it transforms certain kind of ink to energy it does this via runes and tattoos.(They could extract this ink from a special type of Cristal as an essance.) I know how e=mc² works but I don't have any idea about its details.
This 'magic' could used in different purposes:
Lightning and fire for armors, swords, shields, etc.
Heating for smithing tools, swords and armors etc.
Energy shields for armors and castles
Pushing objects and making winds
Power ups like strength,speed and stamina etc.
My main problem is about energy. What would be the total energy of a fantasy lightning etc. How many times could you use it for a energy that equals a gram of matter. How much would teleportation cost.
Explanation for tattoos: They are very similar to others. they basically puts tattoos that represents certain actions like fire, lightning, stamina, strength etc.