[Snake]

That's to make it so you're not the mister all powerful 2M, +25% damage, -25% FP cost flash-spellcasting for standing on something without a few drawbacks, be it you're a tank or dodge-based char.

It's supposed to sharply drop your defenses, AND, sharply increase your offenses. Just like in Final Fantasy, the source of them. And something Evoker might want to have, given they don't naturally offer any defensive options anyway. So further dropping their already non-existent defenses in trade for higher damage is kind of okay, I think?

And in case I misread, the 'friend or foe' part is to make the Leylines an undesirable position to be on, for anything but the creator of it.

And in case you misread, Leylines are supposed to be 1 tile only, the tile directly under you. I don't know how Magnetized enemies will suffer to it.