Empower nerfs

[Lythine]

As fun as empower is currently, it's extremely powerful. There's been a few rounds where wizards made themselves reinforced glass fortresses in commonly passed areas and spammed empower with staff of cthulhu to kill anyone that walks past. It's really hard to counter that.

In my head the changes proposed seem even more powerful than before, but it's hard for me to tell without seeing it used in-game. It just seems like it'd become more of a do-everything spell rather than one for offense or defense, but maybe that's not a bad thing.