To me, Regenesis is a build-around card. There's a huge amount of potential upside here, but with the downside that if you don't set everything up perfectly, it's just a blank 3/1.
The best case of Regenesis
First, let's look at what happens if everything goes ideally (later, I'll look at what's required to make that happen). If scored correctly, Regenesis is a 3/4 agenda; that's 3 advancements and 4 points, the best advancements-to-points ratio Netrunner has ever seen. (Contrast Vulnerability Audit, a fringe-playable agenda which has similar but slightly less onerous restrictions on how to score it, and is a 4/3; one advancement harder to score, and one point less.) It is possible to score Regenesis very early in the game; if the runner misguesses, you can never-advance it on turn 2, and even have some ICE for protection; and you can score it on turn 3 without the need for any bluffing, with ICE blocking all the servers the Runner might have run to disrupt your perfect score (and thus requiring them to find appropriate breakers or some other way to stop the combo, which is hard to do that early in the game).
There's also very little stopping you scoring out a Regenesis combo twice in quick succession – with only basic actions and agendas (and preferably some ICE, which you'll have spare clicks to play), it's theoretically possible to win on turn 4, and a Regenesis deck can credibly threaten this (although it's unlikely). Turn 6 is entirely reasonable, and if my Regenesis deck gets a fast start, that's about when I'd often be winning. This is much faster than "score 7" decks typically go in Netrunner; even typical rush decks are slower than that (a while ago I made a rush deck focused on Ashes Startup, with a set plan for its actions on every turn to make it go as fast as possible, and even that couldn't win until turn 7). By turn 6, many Runner decks haven't even started trying to interact yet, and are still trying to get their economy in order.
As such, Regenesis gives the potential for very explosive starts, to what could otherwise be a fairly slow deck (for reasons explained below, I think the best place to play this is in glacier decks). You also aren't giving up much to run a playset – a common agenda mix for glacier decks is to play mostly 5/3s, with a few 3/1s as the seventh point, so the only actual cost to running a playset of Regenesis is the opportunity cost of not playing House of Knives instead. (You don't have to score Regenesis "correctly" – you can just score it as a normal 3/1 if you prefer.)
A correct Regenesis score is also possible later in the game (it's common for Regenesis decks to score out with 8 points using two Regeneses), but more difficult, as the Runner's clicks normally become less valuable as the game goes on and they're more likely to be able to get into the servers in question.
The requirements to make Regenesis work
It's probably about time that we look at the list of requirements needed for a correct score, to get some idea of the difficulty of setting it up:
- An x/3 (typically 5/3) agenda was in Archives at the start of your turn. That means that either you went a whole turn cycle without the Runner checking Archives and stealing it, or you discarded it during the Runner's turn somehow.
- The x/3 agenda was face-down in Archives. Even if it's an Obokata Protocol that the Runner couldn't afford to steal, checking Archives would have turned it face up. So the runner can't have checked Archives at all since you put it there.
- On the turn you score it, Regenesis has to be advanced to 3 counters without the help of any operations (unless they remove themself from the game). This rules out most fast-advance shenanigans; neither Biotic Labor-alikes nor Trick of Light-alikes can be used to save a click on the score turn, so most likely you need to have had Regenesis in play already.
- On the turn you score it, Regenesis has to be advanced to 3 counters without the help of any trash abilities. This rules out nearly all the fast-advance shenanigans that weren't ruled out by the previous point.
- The Runner can stop a Regenesis combo by somehow forcing you to trash a card in the middle of it. This is possible (e.g. as mentioned in the comments of the other review, Gachapon can install a virus and trigger Avgustina Ivanovskaya), but it rarely seems to be a problem in practice (most Runner decks don't have any combination of cards that can produce this effect).
- You can accidentally mess up the combo by trashing a card for an unrelated reason. As such, you should probably avoid putting cards like Nico Campaign into the same deck as Regenesis.
The "normal" way to meet the requirements on the Regenesis half of things, and my preferred method, is a "basic action score" of the Regenesis: install it one turn, then on the next turn, triple-advance it with an entire turn's worth of basic actions and score. This naturally meets requirements 3 and 4, and 5 isn't normally a problem. Meeting 1 and 2 is more interesting; you have to get a (presumably) 5/3 agenda into Archives face down, without the Runner just running over there and stealing it. There are a few possible approaches to this problem:
Overdraw – if you draw more cards than your hand size, the excess get discarded face down. If you do this by clicking for a lot of cards for no obvious reason and then discarding, runners will get suspicious, so it helps if your deck can naturally get itself into situations where it goes beyond the maximum hand size. Some examples of cards I've found helpful here are Rashida Jaheem and Gatekeeper, which draw lots of cards with semi-awkward timings and where it usually makes sense to draw as many cards as possible and discard the extras. (If you install a Rashida then draw up to 5, the next turn you'll be saddled with a 9-card hand, and discarding from that doesn't look at all suspicious even if you actually had a way to use up four cards in three clicks.)
Another way to stop an overdraw looking suspicious is to use all your clicks scoring an agenda, when you had a 5-card hand at the end of the turn before. Your mandatory draw will put your hand over the size limit, and you won't use up any cards that turn because you're busy scoring an agenda, so the discard will seem natural. The main drawback of this approach is that it's hard to score agendas two turns in a row, so your 5/3 will probably be sitting vulnerable in Archives for two turns rather than one.
Discarding as a cost, in advance – Hansei Review is the most obvious card here, and probably an automatic 3-of in any Regenesis deck; a Hansei Review discard doesn't look nearly as suspicious as an overdraw discard does, and you can do it without having to waste lots of clicks drawing cards (and you get some pretty decent economy in the process!). Anoetic Void also works, as long as you can get the runner to run its server. (The meanest version of this is to install a Regenesis "dry", bait the Runner into its server, then stop the run with Anoetic Void and discard a 5/3 in the process – this requires very good judgement of where the Runner is likely to run and how far into the server they think they can get, and is comparable in difficulty to getting someone to hit an Urtica Cipher in your scoring server.)
Mill – the Runner may be kind enough to trash cards from R&D for you, but if not, there are Jinteki cards that trash cards directly from R&D. Genotyping is a good choice, because its main effect allows you to retrieve Obokata Protocols that are stuck in Archives face up.
Kakurenbo – I haven't tested this, and suspect it isn't good enough (and it's very suspicious if you trash two cards with it and install only one). Even though it does everything that's required to set up the combo on its own, it's at the cost of telegraphing that something is definitely up (because otherwise you might have just IAAed the card you're installing manually). If you decide to try it, feel free to let me know in the comments (or in a separate review) how it went!
Discarding as a cost, immediately before your turn starts – in practice this means Moon Pool, which seems to have been designed specifically to combo with Regenesis. This saves you from leaving agendas vulnerable in Archives at all (rather, you have to keep the Moon Pool safe for a turn, but you're losing an asset rather than an agenda if you fail).
In all these cases, the Regenesis and the 5/3 agenda are each sitting somewhere the Runner could access for a turn (Regenesis in its remote, and the 5/3 typically in Archives; it's in HQ with the Moon Pool method). So pulling off the combo requires that the Runner doesn't interfere. Let's look at how that might happen next.
How the Runner might interfere, and how you can stop them
Unlike most agenda scores, where you're only trying to guard one card (the agenda you're scoring), a correctly scored Regenesis requires guarding two agendas: the Regenesis itself, and the 5/3, which are in different servers. Normally, these will be in a remote and Archives respectively. The Runner can mess up your attempt to score four points by successfully running either server, which is a big difference from something like Vulnerability Audit. In order to keep them safe, there are two main approaches, which are each fringe-viable individually and much stronger when mixed.
One of these approaches is the "never advance" approach. To set up a Regenesis score, you're installing a card in a remote and dumping a card face-down in Archives (often on the same turn, although they can be done separately if you're OK with giving the Runner extra time to interfere). The idea behind this approach is to make those actions things that you do frequently over the course of the game. That card installed in the scoring remote might be a Regenesis, but it might also be a Rashida Jaheem, or a Regolith Mining License, or a defensive upgrade. That card paid to Hansei Review might be an Obokata Protocol, but it might also be a redundant piece of ICE, or a spare economy card, or a Mavirus. That card discarded to overdraw might be a Bacterial Programming, or it might be a mid-value card for which there wasn't enough room in HQ. The idea here is that the Runner has no idea when interfering will stop an agenda score; everything you do looks like it might be an attempt to set up Regenesis, so most of them aren't. If the Runner checked every time, they'd never get anything else done.
In order to make this approach work better, you have to design your deck to find other purposes for putting cards into Archives and into its remote servers. The latter isn't very difficult in most decks; lots of cards go into the roots of remote servers. Finding reasons to put cards into Archives is harder; Hansei Review is the most obvious one. Using an ID that cares about face-down cards in Archives can also help with this; with the current card pool, that's Jinteki: Restoring Humanity, which generally complements a Regenesis deck pretty well. (Spin Doctor also gives you a reason to put agendas into Archives – the problem is that it gives you a reason to put agendas into Archives, rather than other card types, so this won't do much to discourage a runner from running it!)
The other approach is to just keep the Runner out of the server. Glacier decks are used to keeping the runner out of HQ and R&D and the remote (and will normally put a bit of a tax on Archives, too). If you're building your deck around Regenesis, you can just put extra effort into keeping the runner out of Archives. My Regenesis decks are serious about this, and will frequently guard Archives with an Anansi plus extra ICE on top of that – if the Runner wants to get in, it's going to really cost them. One advantage of this approach is that if you're putting enough protection on Archives to prevent the Runner getting in, you can use it as your main location for storing unwanted agendas, meaning that you no longer really have to protect HQ (in effect, giving Archives HQ-level protection means that you can afford to give HQ only Archives-level protection). This technique is a little dangerous, because HQ needs multi-access to hit reliably and Archives doesn't; but if the Runner is running lots HQ multi-access, there's no real downside. (Whether it's better to store the spare agendas in Archives or HQ can thus somewhat depend on what the Runner's deck is like.) Running Obokata Protocol helps to manage the risk here, because if the Runner manages to make their way into an Archives packed with agendas, it'll still limit how many of them can be scored at once.
When you combine these approaches, you end up with a deck which, in effect, is threatening Regenesis scores pretty much every turn, but defending Archives and the scoring remote to the extent that it's expensive to check. If the Runner checks and is wrong, they've wasted a lot of credits and/or single-use effects getting into a server with nothing valuable in it, often opening a scoring window. If the Runner doesn't check and is wrong, you score four points very cheaply. This ends up playing quite similarly to other never-advance decks, but you're guarding two servers rather than one, and scoring four points at a time rather than two.
The Runner can also interfere by trashing a Corp card in the middle of your scoring turn, if they have some way to do that. If Regenesis ever really catches on, that may well be the tech that becomes standard to counter it.
Regenesis needs a lot of support to work optimally. You need a deck that can keep the Runner out of at least two servers (or at least put a large tax on them), and that runs a lot of 5/3s; in other words, this is probably a glacier deck. The effort you'll put into guarding Archives means that your deck probably wants other reasons to keep Archives safe (such as being Jinteki: Restoring Humanity). It'll also dictate some of the card choices you make in the rest of your deck – you'll generally prefer cards that could be placed in a scoring remote unadvanced, and cards that have a tendency to cause you overdraw issues, because those help to make it hard to guess when the Regenesis is coming (whereas cards that trash themselves on a schedule can make it harder to land). You'll almost certainly want a playset of Hansei Review.
However, within those constraints you have a lot of freedom with the general deck style. Pretty much all the cards you're playing to make Regenesis work are cards that wouldn't look out of place in a glacier deck; "lots of ICE, defensive upgrades, asset-based burst economy, and an agenda suite of mostly 5/3s with a few 3/1s" is pretty much a description of a glacier deck as it is, so you can just use the spare slots to actually build the glacier deck. The big difference from normal glacier decks, though, is that it can realistically threaten scoring four points out of nowhere, including in (especially in!) the very early game. It's a strange feeling to have a deck that would look like a perfectly ordinary glacier deck if you changed three card slots (Regenesis for House of Knives), and yet can frequently win games before they've even really got started (faster than even rush decks could typically manage).
As such, the normal Runner counterplay to glacier, of sitting back and building up a huge attack on R&D, doesn't really work; the Regenesis combo forces the Runner to constantly try to interact in order to avoid getting blown out, and that makes the deck works better as a glacier. (I almost said "the glacier half of the deck", but it doesn't work like that – although you are in effect combining two strategies in one deck, the Regenesis combo and the glacier approach, the two strategies almost completely overlap in the cards they use and do similar things with them once the game begins, so it's more like you have one deck that can win two different ways from the same cards and board state, and can choose between them based on what the Runner does.) This is especially powerful because, up until you score a Regenesis or the Runner steals one, the deck doesn't look any different from a regular glacier deck, as hardly any slots are different.
My testing of a Regenesis-based deck is showing pretty good results so far; even though I haven't finished tuning it yet, it's running over an 80% win rate (although I haven't played enough games with it to be confident that that's a "true" win rate rather than a statistical anomaly – Midnight Sun has only just been released). I suspect the win rate will go down if the deck becomes more dominant and Runners adapt to it (in particular, the turn 1 play of "Hansei Review, install card in remote and ice it" can at present frequently lead to four points scored on turn 2, but Runners are likely to get wise to this over time). However, it wouldn't surprise me if it nonetheless ends up as one of the better decks despite that. (That said, there are some pretty degenerate Corp decks going around at the moment, so it's quite possible that they end up dominating instead and the Regenesis deck gets temporarily forgotten until they get banned or Runners work out how to deal with them.)