Adorned Pouncer

Oracle Text
Double strike
Eternalize
( , Exile this card from your graveyard: Create a token that's a copy of it, except it's a 4/4 black Zombie Cat with no mana cost. Eternalize only as a sorcery.)Card Rulings
7/14/2017 For each card with eternalize, a corresponding game play supplement token can be found in some Hour of Devastation booster packs. These supplements are not required to play with cards with eternalize; you can use the same items to represent an eternalized token as you would any other token.
7/14/2017 If a creature card with eternalize is put into your graveyard during your main phase, you’ll have priority immediately afterward. You can activate its eternalize ability before any player can try to exile it, such as with Crook of Condemnation, if it’s legal for you to do so.
7/14/2017 Once you’ve activated an eternalize ability, the card is immediately exiled. Opponents can’t try to stop the ability by exiling the card with an effect such as that of Crook of Condemnation.
7/14/2017 The token copies exactly what was printed on the original card and nothing else, except the characteristics specifically modified by eternalize. It doesn’t copy any information about the object the card was before it was put into your graveyard.
7/14/2017 The token is a Zombie in addition to its other types and is black instead of its other colors. Its base power and toughness are 4/4. It has no mana cost, and thus its converted mana cost is 0. These are copiable values of the token that other effects may copy.
Two, we know its unofficial, the capslocked rant was meant to be humorous in the "the suspense is killing me" vein.
Two, obviously this is an unofficial leak and not an official spoiler, those don't start until June 16th, so complaining about the order is ridiculous.
I wish the FIRST card spoiled with this ability would tell us what it means.
The only keyword I can think of that doesn't use reminder text is transform - because double-faced cards are obvious what they need to do.
For something to be 'eternal' it can't be removed in any way. Something eternal to me winds up being a concept or an idea rather than a physical thing you can interact with.
I feel like these come together to mean that Eternalize cards are double-faced cards with an emblem on the back side of them. They get moved to the command zone and have an eternal effect on the game after they have been eternalized. (Hopefully we'll have a way of dealing with Emblems too - something I've been wanting for awhile)
http://magiccards.info/query?q=o:Transform&v=card&s=cname
How many reminder texts do you see for Transform? None. It's pretty obvious what it does solely based on the fact its a double-sided card. This is why I feel that this might also be a double-sided card. (Being an Emblem that needs to change zones would make it different enough from other transform cards to need it's own keyword)
The card is fully revealed. This isn't a case where WotC has put half the card on their site and hid half of it (as they have done with some cards). We have a photo of the actual cards. It's technically a leak, not a WotC reveal. There is no reminder text on this card (There might be a reminder text in the in-set non promo card, though.)
I am unable to find a case of any promo cards (full art or otherwise) that didn't have reminder text on the keyword except for evergreen keywords or cards that had a lot of other text which didn't leave room for a reminder - neither of which is the case here.
I encourage you to google image search Full Art Promo Cards MTG - you'll see that these do typically waste a lot of space when a reminder text is not necessary. They never have flavour text.
It would seem kinda stupid on WotC's part to introduce a new keyword & NOT have the reminder text on the card explaining the new mechanic to players.
Staggershock has reminder text for Rebound.
Strangleroot Geist has reminder text for Batallion.
Incorrigible Youths has reminder text for Madness.
The only keywords on full art cards that don't have reminder text that I see are evergreen or they fall into the 'too much text' rule where they always drop reminder text (Nighthowler).
Thus, I think my hypothesis stands - it has to be something blatantly obvious along the lines of transform.
Perhaps it does the same thing as Embalm except it includes getting something like Indestructible when it comes back.
I didn't think that would be what it was, though. Seems silly to make a new keyword in the same block to do the exact same thing but make the token black.