I like this.

Definitely a good first attempt at the suggested Volrath's Stronghold variant. However, considering the existence of Mistveil Plains (which you, of all people, should remember), I think you can push it a bit farther.

Also, note that WotC is committed to a sparse usage of the Legendary supertype on lands, a design shift that came about during Zendikar. Valakut and company declared that it was alright to put a proper name on lands without making them legendary.

Maybe use Oust technology to represent that healing duration:

Nils Ossmer Veteran's Hospital
Land
­: Add to your mana pool.
­, : Put target creature card from your graveyard into your library third from the top.

Putting the creature X from the top would more accurately reflect the functions of a hospital and would be a good change.

Not a bad idea, but I want to keep things simple — either it goes on the bottom or it shuffles in, and white seems more orderly than that.

SPOILER ALERT!

The overall story requires a hospital to be involved in the Foehr/Day of Silence level of the conspiracies. Foehr, despite looking like a prime villain due to his aggressive intel-gathering and unscrupulous spy network, is actually funneling resources to a secret operation within a veteran’s hospital in order to find a cure for the crossblight. Don’t scoff, it makes sense:

1) He wants to find a cure because there’s money in the treatment. Not in the cure itself, mind you, the treatment. Same way he got into business looking for a way to control the effects of vampirism, he knows that if his labs have something that the families of the Crossblighted want, he makes money.

2) He funds this work in secret because he has prior knowledge of the cause of the condition — he was part of the shadow team that developed the weapon deployed on the Day of Silence, which has caused a blowback in the form of the Crossblight. Having Aricus work legitimately in the Labs on the cure would hurt him by forcing to admit his complicity in what is now seen as a grand government conspiracy. She would also be likely to bring the full cure to the public, rather than the partial treatment that Foehr ultimately wants.

Houk facilitates Foehr’s access to the hospital resources for similar reasons; he needs a way to neutralize the public image problem of the Crossblight, but also needs to avoid having any official connection to the problem. Ideally for him, some doctor in one of the veterans hospital will stumble onto a treatment that some large, industrial-bio-technomancy company can then mass produce more efficiently than the government.

(See parallels to the U.S. government’s downplay of PTSD for so many decades, or George Carlin’s bit on “shell shock”.)

For these reasons, I think it’s feasible to have the hospital tuck those casualties of these skirmishes away where they’re safe but wont be seen for a while. Things happen in there that Foehr and Houk don’t want you to know about.

Side note: I don’t think this card really needs the flavor text, and I think it might reach across the “awesome line” if it had an evidence trigger. After all, roads are going to point to it in the story eventually...

I dropped the “died this turn” clause to simplify it. Is it needed for clarity of concept though?

I liked the flavor text, but if it's too long, it's too long. If you change the activated ability, make sure to adjust the Evidence trigger to match. They're too similar right now, while working differently. Also, "Veterans'."

The similarity was an editing error. My gut says to make them identical, so that if it gets milled or killed, it still does its thing at least once.

Strangely, it seems like more often than not it's simply "Veterans Hospital", much like how we have the Depertment of Veterans Affairs. I imagine it doesn't really matter, but I hadn't ever thought about it.