Before I forget, again, I wanted to call attention to a funny marketing inadvertence on the back of these MtG books so far.
Naturally, the publisher (not originally Wizards of the Coast by the way, who took over publishing later to set the books into true long-form continuity) was instructed by WotC to market the card game in marketing the books. One form this took was offering one or two free "unique" cards for those who purchased any book and sent in the coupon in the back. (Both of Emery's books had theirs cut out;
Arena doesn't! -- and I was tempted to snip it and send it in, even though the offer has expired literally a few decades ago nOWWWW I FEEL OLD AGAIN AAAHHH!)
Another form, which I suspect (but don't know) is related to that offer, involves the back cover, where beneath about 1/3 a page of plot description there's a depiction of several cards scattered around flipped face down and two face up.
For the first book,
Arena, the cards are "Arena" (a card I think I might own in my collection somewhere) and a black card I didn't recognize. But since one of the cards was "Arena" I figured the second card had some connection to the plot, too.
After finishing Arena, I went back to study that card more closely, and after some squinting I made out the font at the top of the card to read "Sewer of..." some city I couldn't quite decipher. Okay, that made sense: I joked in my review upthread that it seemed like 1 in 5 pages was either set in the city's sewer or might as well be! Being familiar with the tendency to make up foreign/exotic sounding names for places and things on the cards, and not remembering the name of the city anyway, I didn't pursue the matter more closely, but went away satisfied with the cute plot / marketing connection.
Comes the second book, which starts its own separate story, where the connection to Book 1 is just a quick bit of plot-angulation to acknowledge (by what story-trope students now call "lampshade hanging", calling attention to a problematic detail voluntarily) that the wizards of that city and the areas nearby seem to practice magic differently, and that the world of the "Domains" is a vastly larger place than that book's plot suggested, with tons of areas not involved in that story at all. Yep, fine. So out of curiosity, what cards are being presented in the back-cover's marketing tie-in?
... ........ lol! "Arena" and the "Sewers of..." some city card! Wow, the marketing department faceplanted on that one!
Now comes book 3, the second in the current series, and the first thing I do is check the back: there they are again, "Arena" and "Sewers of..."!
Only this time something is different. Something about the sewer card... oh,
they left off the whole title! 
Now, it happens unexpectedly that the author (Clayton Emery), or possibly his publisher or (more likely than the book's direct publisher) WotC, decided to connect this 2nd book in the "Greensleeves" trilogy back a lot more strongly to
Arena, much more quickly than I was expecting, too: the whole second or third chapter hot-patches the first book's plot directly into this story's own ongoing plot!
Huh. So, I guess, in a way the cards on the marketing art in the back do tie in after all? Except no Sewers? -- and only a tangential connection to the Arena now?
The city's name (Etrarsk I think? -- book's in the car at the moment) gets thrown around enough in Book 3 that now I'm wondering if I did see it before in the first book and just forgot it because there were so many exotic place names that it didn't mean anything. (A common fantasy-author problem, one that's hard to work around as I know from experience.) So, huh... why didn't they print that name on the "Sewers" card on the back cover? Was it something else and they now knew they'd have to change it, but the name hadn't been decided on when the cover went to printing (not impossible considering production schedules) and so they just left off the card-title altogether rather than change it?
That led me to look back to Book 2's back cover, to see what the city's name had been.
...
......
OMG, now that I care enough to squint to clarify the name, I can see: it's "Sewers of Cityname"!
I'm not joking! -- I even went back to the first book's back cover, and it's the same thing! "Sewers of
Cityname"!
I hadn't even noticed! I was so used to the name being an exotic non-meaning (to me) that my mind just parsed the city's name as an exotic meaningless name, and I never even noticed the name
is the most generic possible placeholder graphic! 
Whoever designed that back cover, that was pretty dang clever as a desperate trick to get past a production snafu! I bow in your general direction, wherever you are and whoever.
Edited to add: "Estark" is the name of the city; and indeed there was a production card named "Sewers of Estark" -- but not named that on the back of those books.
It's a powerful, but still legal, card, too! It makes any target attacking creature unblockable this turn, or prevents all damage
to a blocking creature regardless of how many creatures it's blocking.
