Added 9 minutes later
Alessia uses a fire rune on a tile two spaces away from Isabella.
Air bypasses Diablo and runs towards Isabella.
Veserod shoots a larval arrow at Diablo.
In general, we're surrounding Izzy. Now, she either has to jump into the arms of the melee units or stand in the area of effect and try to shoot them down. But they have death protection, for such cases, and you can safely cover them with a rune. I wouldn't really want to waste the protection for that, but this is a very tough battle.
Added 2 minutes later
If anything, I plan to pull the melee units out of the area of effect. The words about death protection referred to Isabella's shots. I'm clarifying just in case it was misinterpreted. The words about covering with an area of effect imply those already killed by Isabella, to whom the rune will do no harm.