Reducing defense to a particular element with a special move Options

[sleap]

I can't seem to figure it out, I want to have monsters that fly and are therefore resistant to melee attacks, but then I'll have a character cast "Gravity" or "Clip Wing" and then the flying monster will be vulnerable to melee attacks,

I also need this for an armored enemy and a flying armored enemy

Also a I want the water spell to make enemies weak to lightning