This card is one of the most powerful econ cards in the core set, as it' unlimited economy and this is quite rare. It's nick name is MOpus and is currently on the restricted list. On the other hand it comes with the costs of 2 MU. When you don't have your console you can't have all 3 breakers out, exception is you are Chaos Theory: W√ľnderkind this plays out nice in the revised core set. There are more and more consoles out that provide +2 MU, making running MOpus not such a big commitment.
When you play Magnum Opus you want to get it down Turn 1, so it's usually slotted with Self-modifying Code (install SMC, credit, credit, install MOpus, click MOpus) and often you also see Modded as it reduces the install costs significant. So running MOpus means usually mulligan for it.
With this card out, it's hard for the corp to compete the money game and often this is used for remote camping. So you are running every card installed in a remote and otherwise just click for credits. So it becomes hard for the corp to score an agenda in a remote.
You need to compare MOpus to other econ cards like Armitage Codebusting & Liberated Account and of course clicking for credits. Compared to clicking for credits (counting the install) it pays out at click 7 assuming you have the credits to install it. Compared to Armitage it will have the same efficiency at click 11 and compared to liberated at click 12. After 20 clicks the lead is:

  • Clicking = 20 creds
  • Armitage = 24 creds
  • Liberated = 25 creds
  • MOpus = 33 creds

so you need to click MOpus a lot to make it worth playing. When you install another Liberated fast, the difference is not so significant. It also increases it's use when combined with Beth Kilrain-Chang as another click means you can click it one additional time per turn.

On top, MOpus can be protected by Sacrificial Construct and as currently most decks rely on resources it's not effected by Scarcity of Resources.

When running MOpus you usually can trash every asset installed naked like PAD Campaign so preventing the corp from getting the econ advantage.

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Just to point out, for the purposes of deckbuilding, MOpus should be flagged as being on the current MWL (2.0) —

This is one of the strongest 3 / 2 agendas available and enables the never advance game in NBN. It enables additional shenanigans and is the only agenda that you can use to score and win the game, you need a lot of advancements (13 in total) and usually a tagged runner and Psychographics but it's possible. Hard-Hitting News might already activate it.
It encourages you to use scoring windows especially in the early game, you can score 3 points to reduce the number of agendas you need to score to 2 or in the late game you can use it to close the game. It also forces the runner to run even when they are not ready.

This agenda is called Global Food Initiative 4 - 6 in any NBN deck and this is true! You can install, advance, advance it and score it as a 5 / 3 agenda, while it's only worth 2 points to the runner. Truth is as well, this only counts 2 points to your 20 agenda points, so it's not a GFI in this regards, but on the other side you can also score it as a 3 / 2 and that makes it one of the most flexible agendas in any NBN deck.

If your opponent plays The Source it becomes a 4 / 2 but at the same time it remains a 5 / 3, as you get a counter for every advancement over 3! This is also true for all the other 3 / 2 like Project Vitruvius, Project Atlas and Braintrust

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This is a very interesting card. Play it turn 1 or 2 to force the Corp to decide if they want to defend HQ or R&D and / or give you potential free access on the other Central especially if no Hedge Fund was played so far. On top it takes away the surprise factor and facecheck punishment, additionally in the early game crims can use Special Order to fetch the correct breaker to increase the pressure. On top it might enable Emergency Shutdown so corp rezzes ICE on Remote, you run HQ for free and derez it. So in this it's similar to Maxwell James and both have different purposes.

Playing against Archer this is nice, does the corp want to rez it, when you are not facechecking it? Probably no and if yes, it might prevent you from getting in, but without the corp getting 2 creds and you loosing potentially 2 breakers.

When the Corp tries to score an Agenda, like: Install, Advance, Advance, this card shines. You know they will likely use their creds to defend the remote. Usually you use this point in time to get free / cheap access to HQ and / or R&D. But with an FAO in hand you could use it put them in a lose lose position. You rez the ICE I get the agenda, you don't and you might need to find another ICE to protect this server. On top if the runner runs on a central in such a situation, the ICE might be crippling him and it might become impossible to run the remote (e.g. rezzing Tollbooth might make them lose the creds to install Paperclip & break Vanilla, but not anymore with FAO).

Also in the late game it can create such situations as it might remove 1 ICE from a central and you know the one rezzed is easy to break. But of course there it's more important to wait for the right moment to use it. Of course Los: Data Hijacker makes this even more interesting as it means he get's his ID ability creds without running so it's an auto include combined with Rubicon Switch he can get crazy.

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This card got a new best friend named Bryan Stinson and thus it creates multiple win win situations. It's a must trash asset which is good and on top it's a trap you can't ignore. When you get it into a taxing remote you win either by the runner not running it and you can bankrupt him or by running it and bankrupting himself with your taxing ICE + the trash costs, either is fine from the corps point of view. The runner losing 4 Credit's per Advancement is great too.
On top of that when you have bankrupted the runner you can fire cards with Bryan Stinson like :

And especially in Cerebral Imaging: Infinite Frontiers you can fire cards like:

so in CI you can trigger them both in one turn, making them incredible strong and dangerous. Thus you can find them in the World Championship Deck 2017.

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This is a natural combination and a support card for Los: Data Hijacker as he get's 2 creds for the first ICE rezzed per turn the likelyhood you might come out of this ahead is great as derezzing means you will get the Los bonus again (and again and again). Of course this makes most sense if there are more support cards that benefit from rezzing ICE such as Compromised Employee, Keros Mcintyre, Collective Consciousness and Ice Analyzer (together with the bird breakers).
This can create situations where the corp don't want to rez ICE anymore which is something you will like to as it means runs are for free and you can save your resources for the times you really need them and you avoid situations as a criminal where you are locked out and your engine is not going anymore.
The downside is, that you need a click to do this, which is different to the bird breakers and you can only do it the turn the ICE was rezzed. So you will need other tools like Emergency Shutdown and Crescentus to get ICE derezzed again to bring it back to Rubicon Switch range.
I think it's more a tool for the mid to late game where you can avoid runs becomming to costly and make it uninteresting for the corp to rez ICE as they know what will happen, which is a positiv thing ;-) combine this with The Gauntlet they will think about rezzing ICE, know you can break it, get creds for it and will see an additional card and afterwards might derezz it again....

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En Passant could be used to trash derezzed ice. —