ZATO City Grid is a defensive upgrade that has quite a lot of potential, but is also pretty clunky to use. As far as I can tell, there are two main ways to use it: a) as a source of semi-repeatable unbreakable " End the run." (ETR) effects or b) as a way to fire high-impact subroutines without having to rely on the Runner faceplanting into them.
Looking at the first mode first, ZATO City Grid can do a sort of Anoetic Void impression via making all your ETR ICE into a sort of poor corp's Border Control. It isn't nearly as strong as Border Control, because you can wait to use that effect until the Runner's passed all of your ICE (thus forcing them to spend their way into the server). It loses even further to Anoetic Void, because you can wait to use that effect until the Runner approaches the server, a timing which allows Void to combo with Manegarm Skunkworks and/or Formicary. The advantage over Border Control is that you can fire it multiple times in a turn by trashing multiple ICE, and the difference with Anoetic Void is that firing it multiple times consumes a different resource (rezzed ETR ICE rather than 2+2 cards).
As such, using ZATO City Grid to defend an agenda is somewhat reminiscent of playing an AgInfusion: New Miracles for a New World glacier deck. Ag glacier was one of the top Corp decks for quite a while (and is still playable), and scores agendas in the late game via stacking enough unbreakable methods to prevent the Runner breaching a server that they run out of clicks trying. Perhaps the first time you try to run, you hit a Border Control; the second time, you get thrown to Archives by Ag's ability; the third time, the run is stopped by Anoetic Void; the fourth time – wait, did you have enough credits to get into the server four times without even spending a click to prepare? I guess I'd better use my Nisei MK II, or my Sand Storm, or sonething. ZATO City Grid, in the late game, effectively lets you do the same thing out of a Weyland deck; you might not have an ID ability that directly helps, but you don't need to find 3–4 different ways to end the run, you just need 3–4 ETR ICE rezzed on the server. Of course, this will only work in a deck that naturally can build a server of 3–4 rezzed ETR ICE, which is unusual, but isn't unheard of; this is a plausible late-game setup for three different strategies (glacier, rush, and rigshooter decks – the rush deck probably didn't want the game to reach the late game, but can nonetheless build itself a pile of ETR ICE as a plan B if it fails to win early on, and often doesn't have any better alternatives).
Is ZATO Grid good for this purpose? I suspect that it is at best a plan B. If you're trying to do an impression of the infamous Haas-Bioroid: Precision Design rush deck, scoring behind a small pile of ICE and a big pile of upgrades, there are much better options (like the infamous Manegarm Skunkworks / Anoetic Void combo); and although those options have weaknesses of their own, ZATO City Grid doesn't really fix any of those weaknesses. On the other hand, if your deck's natural plan is to win via some other method, and that other method naturally tends to build (or can cheaply be modified to build) large servers in the late game, ZATO City Grid can give it an alternative path to victory by only spending a card slot or two. Diversifying your win conditions is usually worth it if you can do it cheaply – many Runner decks will be great against some of your win conditions but poor against others – so being able to use just one or two card slots to gain a late-game way to blow up your scoring server in order to forcibly score an agenda is generally a good trade.
A good comparison is Audacity (which blows up your hand to score an agenda). Some fast-advance decks are built around Audacity, because it's a really strong card; but most decks can't afford the downsides of playing an Audacity in the mid-game and leaving themselves vulnerable. However, even for decks that couldn't survive after playing an Audacity, a 1-of Audacity can nonetheless be worth it as a way to get the last couple of points scored when the deck is otherwise running out of steam. ZATO City Grid plays similarly, but can work with larger agendas (4/2s and 5/3s are just fine because you're planning to score the agenda over multiple turns anyway) – "all" you need is a pile of rezzed or rezzable ETR ICE on the server.
Of course, just firing ETR subroutines, while practical in some circumstances, might seem like a waste of the potential of a card like this. Many impactful subroutines are balanced by the difficulty of firing them; one particularly commonly seen pattern is for the subroutine to do something that doesn't matter in the early game, but to have no real chance of firing except on a face-check (and the Runner is unlikely to faceplant into your ICE once the early game is over). As such, the game has lots of ICE that isn't really very useful because it only really functions in a situation that's unlikely to ever come up.
ZATO City Grid can be thought of as giving this ICE a reason to exist. Something like Zed 2.0 has a great subroutine (everyone wants to be able to blow up Endurance, right?), but is incredibly porous in the early game and unlikely to fire in the late game (you can't actually blow up the Endurance because it'll just break the subroutines). ZATO City Grid, by force-firing subroutines, can give you a way to actually fire these subroutines for once. The primary problem is, this still isn't necessarily going to be very good – if you decide to use ZATO on Zed to get rid of an Endurance, you've just spent 9 to get rid of an 8 card, and spent two cards and two install clicks on top of that, and probably several more credits installing additional ICE on the server. So you're behind on economy, and the Runner is still running into what is presumably your scoring server (if you try this on a different remote server the Runner probably won't ever run there), and you didn't really do much permanent damage because Endurance is normally run as multiple copies. Similar reasoning applies to firing, e.g., bulk net damage subroutines (Bathynomus), which could win the game but is more likely to fall flat,
However, there is one fairly common subroutine that does make sense for this sort of combo: " Trash 1 program.". This is a sort of perfect storm of "useful outside the ZATO combo" and "worth it when used with ZATO":
- Program-trashing ICE is generally useful in rush decks (except against Anarchs who rely on conspiracy breakers like Black Orchestra), because it acts as a pseudo-ETR when combined with an actual ETR ICE (normally a code gate because almost everyone is running Paperclip and it's hard to ETR with a sentry). The idea is that you have your program-trashing sentry in front of a run-ending code gate (say Thimblerig or Magnet), as a form of gear check that keeps your server safe until the Runner finds their killer; if they attempt to run the server without the appropriate breakers, you trash their decoder and now they can't break through the ICE behind. So although the subroutine isn't spiky in the very early game, it's nonetheless useful in helping to keep its server safe.
- Against some decks, trashing a program can be really high impact, sometimes effectively winning the game on the spot. Against Anarchs, the impact isn't too great, normally just disrupting their economy a little, because they can normally reinstall their breakers from their heap, so you're either forcing them to pay to do that, or just destroying economic programs directly. Likewise, the various Apocalypse decks tend to have plenty of spare breakers because they're planning to blow up the board themselves. However, Criminals often only run one of each breaker; blowing up their Amina or Cat's Cradle can make all your code gates impenetrable for the rest of the game, so all you need to do from that point is to find enough code gates to beat their bypass effects and Boomerangs. Shapers are a little better at recovering from trashed breakers, but often run very light on ways to recur them nowadays (and if you can trash the World Tree from the 80-card Kabonesa Wu deck that's going around at the moment, the deck will have extreme difficulty trying to draw into a way to get it back). So even if you need to do something janky in order to get the subroutine to fire, there are plenty of matchups where the payoff is worth it.
- ZATO doesn't care about the strength of the ICE you're using – the relevant factor, other than its subroutine, is its rez cost. With many types of subroutine, this would introduce tension between running cheap ICE (good with ZATO but useless without as it isn't very taxing) and expensive ICE (taxing, but a big loss to trash to your ZATO). With program-trashers, though, the cheap ICE is just as good as a gear check as the expensive ICE is.
The upshot of all this is that, unlike with most non-ETR subroutines that you might want to use with ZATO, you can find program trashes on ICE that wouldn't be embarrassing when the ZATO isn't there. Something like Sapper is perfectly viable for forcing a killer install (when stacked with a code gate on your scoring server), and great when used with ZATO because it only costs 3. If your deck is naturally running that sort of ICE, then adding ZATO to its server will give it a new lease of life once it no longer works as a gear-check, perhaps giving you a scoring window or even winning you the game out of nowhere.
All this discussion of the upsides of ZATO so far has, however, neglected a serious downside that needs to be mentioned in any review. The elephant in the room here is Pinhole Threading. "Dies to Pinhole" has become a bit of a meme, because it applies to such a lot of cards – and the primary purpose of Pinhole is to get rid of defensive upgrades like this one, so you'd expect Pinhole to beat it – but the problem is that Pinholes are close to mandatory for many decks in the current metagame, so you're very likely to run into them, and it's hard to justify a strategy based around ZATO City Grid when your opponent can just Pinhole the Grid away and cause your strategy to cease to function.
It isn't just a case of "this is a defensive upgrade so Pinhole beats it", though – ZATO is even worse against Pinhole than upgrades normally are. This is partly because ZATO is limited to defending remote servers, so it can't do anything to help stop the Runner Pinholing through Archives (whereas the other similar defensive upgrade we got in Parhelion, Nanisivik Grid, is very good at defending Archives and so you can use one Nanisivik to help out another). It's also partly because ZATO cares about the ICE arrangement of the server it's trying to defend (unlike most defensive upgrades, which don't care at all); as such, setting up a ZATO means investing resources into getting your scoring server just right, and if the ZATO gets Pinholed, all the resources you spent on that are worthless. And it's also partly because unlike other defensive upgrades, ZATO can (sometimes) defend a server even with no other upgrades helping it, which means that it often has to try to do the work by itself, and if it gets Pinholed, the server is now much less defended rather than slightly less defended; this means that it can be very hard to tell whether you have a scoring window or not, and thus rather raises the risk that you'll try to jam an agenda, only to have your ZATO Pinholed and your agenda stolen.
A secondary downside is that ZATO is pretty similar to Nanisivik Grid, which is somewhat easier to use and which has already found a home (in the AgInfusion glacier decks which were mentioned earlier). Nansivik Ag is a strong enough deck that some Runners have taken to making weird card choices in an attempt to beat it – things like Tracker which previously weren't seeing play at all. Because the two Grids have such similar rules text, this leads to some amount of "splash damage" in which tech cards being used to beat Nanisivik are also capable of beating ZATO, so you don't even get the "maybe my opponent's deck will be unprepared for this" factor that you'd normally get when running an unpopular card.
So is ZATO unplayable? I think it might be in most identities, but it can be somewhat redeemed by the ID it was probably designed for, Ob Superheavy Logistics: Extract. Export. Excel.. The obvious combo here is to use ZATO's trash to trigger Ob's ability; there are some janky suggestions in the other review for particular combinations you could use, but even something simple like "trash Ballista to trash a program, installing Border Control," can easily keep the Runner occupied for long enough to let you finish scoring the agenda that they were trying to steal (and is probably more effective). However, this specific use of Ob's ability doesn't do anything to stop you being Pinholed.
The redeeming feature comes in the less obvious combo – instead of firing Ob's ability with ZATO's trash, what you can do instead is to use Ob's ability to install the ZATO mid-run. Like all operations, Pinhole Threading costs a click to play, meaning that it can't be played in the middle of a run and you need to make time in a turn to play it. When you're trying to steal an agenda, every click counts – so if you install ZATO mid-run using something like Border Control (which pretty much any Ob deck should be running at three copies), the Runner will have to take a click off to Pinhole it before running back onto the server again, effectively allowing one Border Control to eat up two clicks. The great thing about this is that you don't need to draw the ZATO or spend a click installing it; all you need is to have it in your deck. (In fact, you'd rather prefer for it to still be in your deck so that you can search for it – this leads to an odd sort of deckbuilding requirement in which it's probably right to include multiple copies to increase the chance that one of them is still in your deck in the late game, weirdly mirroring the principle via which some cards are run as several copies to increase the chance that you see one early.)
It's possible to do better than this, though – instead of using Border Control to install ZATO City Grid, you can use Stavka. The idea is to wait until the Runner is locked into encountering an unrezzed Stavka, then rez it, trashing a rezzed 4 card (e.g. Mausolus, or a second copy of Stavka). You can then trash Stavka to ZATO, trashing one of the Runner's programs, and without the Runner having any opportunity to Pinhole it at all. (Against most Criminals and some Shapers, the missing program will probably also force them to jack out, so it's possible and even reasonable to do this in the middle of trying to score an agenda.) Although this combo might itself be janky, its components (other than ZATO) aren't, being perfectly reasonable cards to run in glacier or rigshooter. So it's possible to be playing what looks like a perfectly normal deck, then suddenly go into jank mode out of nowhere, trash a critical program with a ridiculous combo, then go back to sensible Netrunner again and finish scoring your agenda.
As a consequence of all this, I suspect that ZATO City Grid may be viable in some decks. However, it isn't remotely dependable. One of its biggest downsides is that it has a more serious case of Pinholitis than perhaps any other card; it also tends to get hit by tech cards that Runners are running for other reasons. Additionally, both of its main uses (destroying programs, and taxing the runner out of clicks during an attempt to steal an agenda) are somewhat situational; you're paying quite a cost to make use of them, and although the benefit you get from paying that cost might be worth it, it also might not be. In order to make it worthwhile, therefore, I suspect that it needs to be placed into a deck that can take advantage of both of its major modes and can also help patch up the Pinhole weakness somewhat – and even then, it's the plan B, not the primary strategy.
Fortunately, decks like this do seem to exist. "Toolbox Ob" has quickly become an established shell for a deck, and is typically quite happy to play situational cards. It generally has rushing as at least one of its plans, which naturally pushes it towards playing lots of ETR ICE; and it also pushes it towards having a range of ICE types at a range of costs (which in turn means that it's usually running Sapper, which is the best 3 sentry for non-Jinteki rush decks). This sort of deck is a perfect fit for ZATO (I already had one built prior to Parhelion's release, and ZATO fit right into it without needing to change many card slots). Despite that perfect fit, ZATO City Grid hasn't been amazing in my testing, but it has at least been doing enough to justify its slot. This does, however, make me suspect that the card isn't strong enough to justify a slot unless you're already running the sort of deck for which everything likes up perfectly – after all, even if you are, the card merely becomes decent rather an an all-star.
It is, however, quite a lot of fun (when it doesn't just get Pinholed)!
