{} is a compound invented for the game, which is why you won't find it in any dictionary.
The reason the second character is difficult to find is that is a rare variant of the more common ("bright, dazzling"). Even if I had never seen the character , I would be likely to guess the reading by interpreting it as a . It seems like a stretch to translate it as "magic light", but since this is a fictional term of art, some poetic license is probably appropriate.
Given the appearance of mako in the game, is probably intended to suggest brightness and brilliance. As you observed, suggests {} ("magic") as well as the meanings of spirits in the context of the game.