Blue doesn't normally get this kind of effect. Planar Chaos is not good precedent.

Planar Chaos' whole idea was to stay within the color pie but see what wasn't used often.

Not quite. Planar Chaos was to stay within the "crust" of the colour pie, but not the "mantle", to use Maro's confusing terminology. It was exploring things that the colours could do in an alternate universe. There's a reason we don't see black getting tappers like Rathi Trapper, or red getting bounce like Stingscourger, or red getting reach like Needlepeak Spider.

It's the most colour-bleeding set in Magic's history, and is explicitly stated to not count as "precedent" for an effect being present in a colour unless the card gets reprinted elsewhere. (Which has happened in a number of cases. Mesa Enchantress and Prodigal Pyromancer replaced their original versions. Red gets more trample now and green gets more haste now.) But some things like black tapping, white countermagic, red bounce, and blue discard are not within the normal colour pie.

Alright. This OK in mono black?

Yeah, I think this is okay in monoblack. It's a bit of a weird take on Mind Rot, but that's fine.