I would phrase this as "Exiled cards can't leave exile". Very nice design: very simple, with some ostensible uses (hose suspend or rebound), and plenty of other uses (my Turn to Mist, Journey to Nowhere, Fiend Hunter etc become way better - in particular Mistmeadow Witch and Roon of the Hidden Realm are suddenly very strong indeed).

I thought this was the clearest possible wording, but yours is also a sensible option.
This hoses all sorts of things, and combos with even more, probably. People trying to use Cascade or Madness would be upset to see this running around.

I like the new name, and the companion cards.

I keep feeling like this must have a really broken combo somewhere but I can't find it. Something like Knowledge Pool is a complete lock against spell-casting, but it's symmetric so you need a way round it (and it costs 6, and it's just one card so one or other could be banned in modern, the question would be more, if there's a problem which effect would wizards want to print more in future).

See Warden of the West and Warden of the South for the other cards in the cycle to which Jack V is referring.

I just edited the cycle so that they use White's shared keyword with the color each references with its cardinal direction.

This card has the most obvious combo potential, while the others are just hate bears.

Thanks for the compliment, Jack. The interaction with Knowledge Pool is unpleasant, isn't it?

Honestly, it's not as good with repeatable flicker effects like Roon because it counters your own stuff too. A lot of nonsymmetric versions for that deck exist already (Sundial of the Infinite, Dismiss into Dream, etc).

Does Dismiss into Dream feel like a color pie bleed to anyone else?

Hm. It SHOULD do, allowing much (unpreventable) destruction of creatures. But it feels right to me -- what other colour would it go in? :)

ETA: I forgot Horobi, Death's Wail. Maybe it should be black, I agree it makes sense there as well.

It certainly fits in blue flavorfully, and mechanically it's not technically doing anything blue can't do. It just puts the two parts together in a way that ends up getting off.

I created Peculiar Illusion with that idea. I think the general principle is that it's ok for a colour to have two effects on different cards which combine to make a non-in-pie effect. But they shouldn't be on the same card. So illusion is not out for that reason.

But it might just not be in pie at all. Not every colour drawback is in-pie when applied to an opposing creature, even if the flavour works.