I was having trouble coming up with an instant or sorcery for this spot. Eventually I decided to look to the story and thought about Khzgeru being outcast from his cackle. The first ability represents Khzgeru's exile from the Bone-Crunch cackle. That ability is totally white (or supposedly blue) though.

I figured a good balance would be to make an ability for Khzgeru then. This ability is mono-black which fits to balance the first, as well the fact Khzgeru doesn't use white mana.

I would make this less narrow. As is, it does nothing without planeswalkers, which I think should be avoided. What if it included creatures? By the way, I don't really see how that first ability is blue.

Made it planeswalkers and opponents on the first option. Blue is supposed to get protection from things other than colors (and creatures I guess), but the only example that comes to mind is True-Name Nemesis.

Blue does get "weird protections," it's true.

"Protection from opponents" is a somewhat confusing phrase. Normally protection from a specific game object means that object can't target/damage/etc you, but in the specific case of players (with only True-Name Nemesis as precedent) it also somehow applies to all spells, abilities and permanents that player controls. So that first ability is actually going to be pretty close to "you and permanents you control gain protection from everything you don't control". In particular, there's no need to mention planeswalkers there any more, as all it does is stop you targeting your stuff with beneficial abilities from your own planeswalkers. (It'd protect your stuff from planeswalker Earthquake effects, if there were any, but there aren't.)

On a rare that might be okay, but just to let you know.

I would say that two mana is too cheap for this kind of flexibility.