Adding a review as there isn't one at the time of writing.

Hammer is AI hate with extra upsides. For those new to Netrunner, there are three basic types of ICE: Sentries, Barriers and Code Gates and three corresponding Icebreakers that can break subroutines on the associated ICE, Killers, Fracters and Decoders respectively. However, there are also AI programs, that can break any type of ICE, but usually have some special rules to limit their power. Still, some AI breakers are incredibly powerful and the Corps form of counterplay to these AI breakers are pieces of ICE like this, ICE with special rules to make it impractical to break it with AI. If this card were "balanced" we would expect it to be painful but not insurmountable for AI-reliant runners, but be slightly subpar against regular Killers.

Since AI programs are usually not also Killers, you can only break one subroutine on this piece of ICE using an AI breaker, which guarantees at least 2 of the subroutines firing. As long as you didn't run on your last click (you shouldn't be running on your last click anyway), a tag is removable and almost always a lot less painful than losing an already installed resource, piece of hardware or program. This means that this card comes down to the question for the runner: do you have a more valuable resource/piece of hardware you want to protect or a more valuable non-conventional breaker program you want to protect? Either way, this is terrible for the runner, if they break the program subroutine they risk losing a critical resource like the The Class Act or The Twinning or they risk losing their console or a critical MU providing tool like DZMZ Optimizer or another important piece of hardware like WAKE Implant v2A-JRJ or Docklands Pass. If they break the hardware/resource subroutine then they risk losing a program, presumably the AI breaker in question, though the Corp can also target non-breaker programs like Cezve, Paricia, Fermenter or even Self-modifying Code. Plus taking a tag in either situation to boot. Definitely a nasty surprise.

This card also has some very nice externalities due to its wording, think Boomerang, Botulus, Rielle “Kit” Peddler: Transhuman, Pelangi, Egret, you start to get the idea, a lot of the runner's creative tools to break Sentries without Killer's start to look a little sketchy.

However, bypass effects do still work, Physarum Entangler, Laser Pointer, Inside Job, S-Dobrado, Backstitching and Alarm Clock can all still completely bypass Hammer without ever needing to technically "break a subrountine."

The next major downside of this card is that it is a pretty pathetic early-game face check. If the runner has no programs, hardware or resources installed, running first click on their first turn, they're probably very happy to see this, because if you didn't already know, 6 credits is not the market rate for a tag. Quite frankly, whoever sold you this is ripping you off because you can get a tag for 1 or 2 credits: Ping, Virtual Service Agent and Vasilisa all come to mind and even something like Funhouse is much better value.

But assuming the runner does have installed cards they want to protect and assuming the runner already has their Killer, what kind of costs are we looking at?

• 5 credits for Carmen (3/5 to Install)
• 2 credits and 3 hosted power counters for Revolver (2 to Install)
• 9/6/3 credits for Echelon (depending on the number of installed Icebreakers) (3 to Install)
• 4 credits for Orca (plus you get to charge another card) (10 to Install)
• 6/4 credits for Ika (depending on if it's already hosted) (0 to Install)
• 3 credits for Afterimage (requires stealth credits) (or 2 credits to bypass, still requires stealth credits) (4 to Install)
• 6/3 credits for Na'Not'K (depending on the number of ICE protecting the server) (4 to Install)

Also worth mentioning that Mimic can't break it without assistance and Femme Fatale breaks it for 7 credits but that's somewhat beside the point of Femme. Also at the time of writing Bukhgalter is banned but if it wasn't it would break it for a net expenditure of 4 credits if that's the first Sentry.

All in all I'd say that this worked out pretty much as expected, ingnoring fringe cases like installing an Orca from hand (rather than with Spark of Inspiration) or a solitary Echelon or this being the only piece of ICE against a Na'Not'K this doesn't exactly break the bank. Against a runner with a Killer this is hardly the most taxing piece of ICE and as we've established it's pretty meek in the early game.

An advanced Colossus can tax the runner a lot more, with similar levels of damage if it's subs fire, Saisentan is still probably one of the most terriying cards in the game for just killing an overeager runner and Winchester gives you the same strength and number of subs, with similar levels of damage if they fire for 2/3s of the cost (asssuming it's over HQ).

Thematically, though, this card really hits the mark, see you can try all of your little tricks and bring all of your little AIs and you may think that you're sooooooo smart with your viruses and making my ICE think that it's something that it's not but let's see how well you deal with a freaking Hammer to the face. Plus the art is awesome, showing the thunderous moment when the Hammer strikes the Anvil. Oh wait, Anvil, despite being released in two different Cycles and having 2 very different effects and use cases, this is a nice extra little easter egg, the Anvil sets them up and the Hammer strikes them down.

If I could make one change to this card, I would probably have made the tag subroutine something else, like an End The Run or maybe dealing 3 net damage. Something just as punishing as the other two subrountines, so when you try to break it with something other than a Killer you either sacrifice a program and a hardware/resource to continue the run, or protect one and lose the other while being unable to get in. It also doesn't make a lot of thematic sense why a Hammer would be tagging you...

TLDR: Considering our starting premise, I'd say that this card pretty much hits the mark in terms of balance, there are better options against true Killers but this is quite punishing against runners relying on AI or other non-Killer tricks. On the whole, whether you choose to include this card is a matter of meta and playgroup, if the meta favours AI and Botulus and the like, this looks promising, if one of your friends you regularly play with loves Aumakua Crim then consider including this card to really mess with them, otherwise, there are probably better options for a standard Corp deck.