Need triggers for this or no?

I want to make two different buffs, that work like Roar, i.e. the hero casts it on himself. One makes the hero immune to physical attacks, the other makes him immune to magic attacks. I was wondering if there's a way to make this just using the buff/ability editor. There's anti-magic shell for magic attacks, but I don't know if it's possible to make the unit cast it on themself. Also, I can't seem to find any ability that just prevents physical damage.

Ideas?

If you can't find something better for physical damage, I suggest using Banish and changing the bonus healing/spell damage etc for ethereal to zero. I think you can use Gameplay Constants for both.