See Challenge # 112. I didn't think I'd ever end up making a white Pale One, but it happened. I wanted to show a Pale One just eating anyone that ventured out into the wastes and came across it. I wanted the victim never to be heard from again. That brought me to exile which brought me to white (I considered red but red exiles after dealing damage).

Mechanically this ability is really threatening as it kills bounce effects. I don't know if it needs to be reworded but I also mean for it to perma-exile something that would be flickered.

Unfortunately, I don't think this permanently exiles things that would be exiled anyway. It's similar to the interaction between Obzedat, the Ghost Council and Whip of Erebos. Obzedat gets to come back forever because it can exile itself with its own ability.

That said, fun card! I was super excited to see a lammasu in Khans of Tarkir, and I'm just as excited to see one here. The art for Venerable Lammas does look quite creepy, as the Pale Ones probably do.

I changed the text to state that Pallid Man-Gnasher exiles the creature instead. Does that change things?

Borrow your wording from Whip of Erebos: "If a creature with power less than ~'s would leave the battlefield, you may exile that creature instead of putting it anywhere else."
I don't think that will stopper things like Cloudshift, though.

Indeed, it's very hard to interfere with Cloudshift.

How about "instead put it on the bottom of its owner's library"?

I like the concept of this card. Somehow the creepy nature of the pale felt quite white to me, although maybe I'm just misled by the name.

I'm surprised that exiling-by-something-else isn't replaced by exile-by-this on things like whip of erebos, the rulings make it clear that's what happens, but it doesn't seem how replacement effects generally work...?

It's because the ability of Cloudshift or Obzedat, Ghost Council looks for the card in exile... and finds it! Because whether or not it was exiled by the thing that was trying to exile it, exile is where it ended up, so the "return" half is able to work just fine.

Oh! Agh. I guess I see. I thought the whole point of the sad linked-abilities rule was that cloudshift would only return the card exiled with that ability. But I guess the way it's worded, it just returns that card, regardless of any other considerations :(

I want to say "if a creature would leave the battlefield, tear it in half" :)

I changed it to Alex's suggestion due the discussion.