Ob is, at the time of writing, easily the most complex identity in standard, not just on the Corps side of the table, but in general. With the sheer number of possibilities opened up by its text box unmatched by any single other ID, perhaps not just in standard but in all of Netrunner's history (see Eternal), though CI might give it a run for its money, albeit for very different reasons. With time, you'll come to see Ob as a collection of combo lines that you'll need to learn if you can hope to master it, or even simply play against it. The goal of this review is to provide, as best I can, a comprehensive list of the most notable combos that can be done in standard at the time of writing, both as a resource for new players and as a mental exercise for myself. This will inevitably change over time, either as new cards are released or as rotation and banlists strip cards away, in fact, even Ob itself may come to be banned in due time, so for posterity's sake this review is being initially written as of the 25.04 banlist (no change in gamestate has been removed as of the time of writing).

Fundamentals

Obs ability to tutor does four main things for you.

1. Influence Saving, for example where most Corps would feel the need to play 2 The Holo Man to find it consistently thus spending 6 influence outside of NBN, Ob can get away with 1 since they can tutor it so consistently, and thus save themselves this influence. Similarly a Ob deck with 1 Phật Gioan Baotixita and at least 2 Cybersand Harvester is almost as consistent as a Jinteki deck with 3 Phậts.
2. Incidental Value, when you play cards that already have inherent value for most Corps but trash themselves once emptied, you can generate some extra incidental value on the back end of this (think Regolith Mining License or Anthill Excavation Contract etc.).
3. Consistency, by including tutors in addition to the cards themselves you're able to establish your core gameplan far faster and more consistently than comparative decks
4. Tricks, this is a catch all term for combos that only work in Ob, think Stavka + Hafrún, tutoring a Spin Doctor off of Slash and Burn Agriculture + Azef Protocol things like that.

But it's not without its drawbacks, Ob has three main drawbacks that can cause problems for them and that'll you need to be aware of if you want to beat them.

1. Deck Thinning, by repeatedly tutoring instalables out of your deck you "thin" your deck, irrevocably increasing R&D's agenda density over the course of the game. This makes you very soft to R&D multiaccess once you reach the late game and often puts you on an implicit "timer."
2. Fragility, it's entirely possible to draw your cards in the wrong order, if you draw your Hafrún it's not possible to pull of the Stavka combo from hand, and you may need to expend your precious recursion from something like Spin Doctor just to get the Hafrún out of your hand and back into your deck.
3. Cheapness, many of your staples are very cheap cards, there simply exists far more options for trashing 3 cost cards to fetch 2 cost cards and so on and so forth than there are ways to trash 7 cost cards to fetch 6 cost cards. This tends to lead to Ob decks playing quite cheap ice, pushing them towards Rush and Asset decks, although some attempts at glacial Ob have been made in the past.

Unconditional Tutors

There are two notable unconditional tutors in standard Mavirus and Cybersand Harvester. These assets can trash themselves at any paid ability window and will allow you to tutor for any 2 or 1 cost card respectively.

2 Cost - Manegarm Skunkworks, Hafrún, The Holo Man, Tucana, Regolith Mining License and a slew of 2 cost gearchecks like Kessleroid, Descent, Flyswatter and so on

1 Cost - Phật Gioan Baotixita, Bladderwort, Tranquility Home Grid, Humanoid Resources, AMAZE Amusements, Wall to Wall, Hearts and Minds, Malapert Data Vault, The Powers That Be and Tithe have all shown up in Ob decks at one point or another and are worth considering.

You can also cascade a Mavirus into a Cybersand Harvester into a 1 cost over the course of 2 turns as well if you really need a specific 1 cost.

Conditional Tutors

These are primarily cards that trash themselves after emptying, thus giving you an Ob trigger, but only if you can protect them for the requisite amount of time. There are many of these, such as Otto Campaign, Nico Campaign and so on but the three most notable that see play are Anthill Excavation Contract, Regolith Mining License and Humanoid Resources.

In addition to the existing ability to tutor 2 and 1 costs, Humanoid Resources opens up the ability to tutor 0 cost cards, notably:

Spin Doctor, Svyatogor Excavator, Angelique Garza Correa and Mitra Aman.

Lamplighter falls into this category since it can and will conditionally trash itself. The only notable combo I've seen pulled off with this so far is that if the runner steals an agenda from a server protected by Lamplighter you can fetch an AMAZE Amusements and present a "surprise" 2 tags that the Runner may not be prepared to deal with. However, it's worth saying that if you tutor 1 cost cards like Phật or Powers they will not "see" the score that trashed Lamplighter and thus will not immediately fire (unlike Azef Protocol which occurs before the score).

Envelopment is also technically a conditional tutor since it can trash itself, but as this is attached to a subroutine, it will only happen when and if the Runner wills it to.

M.I.C. can be used to trash itself during a run, allowing you to get a 5-cost card in the process. But anecdotally, this is far less common than the ubiquity of the now rotated Border Control.

Catalysts

These are cards that trash another card, usually for some benefit, but, by getting the benefit on the catalyst itself and the Ob trigger, you double dip on value.

• Extract is a lot of money (6 credits, 2 more than Hedge Fund) but it can also be used for tutoring.
• Svyatogor Excavator can fire repeatedly if left on the board, both making you money and assembling your game plan.
• ZATO City Grid can be a powerful defensive upgrade, or a powerful "offensive" upgrade used to rig shoot.
• Stavka is the catalyst for the Stavka + Hafrún combo, but it can also just be used in general to get a very efficient one time sentry while firing Ob
• Azef Protocol requires you trash an installed card as an additional cost to score it, but this too can fire Ob

The most notable Azef combo involves fast advancing it with Slash and Burn Agriculture and trashing a 1 coster to fetch Spin Doctor and immediately save the Slash and Burn Agriculture in Archives. However the ability to tutor other cards like Tucana, The Powers That Be or Phật Gioan Baotixita which then still "see" the score, as the trash occurs before the score are also notable as they can allow you to immediate get the pay off from the clickless install from Tucana or Powers or present as surprising burst of 3 damage that the Runner may not be prepared to survive.

Ammunition

There are a notable handful of ice which have powerful effects when rezzed, Obs ability to tutor these at unconventional times can have very powerful, sometimes even deadly effects.

• Ping can tag the runner.
• Flyswatter can purge.
• Bumi 1.0 can trash a trojan.
• Anemone can do 2 net damage.
• Hafrún can disable a breaker.

Some of these can be found using Mavirus, others will need a mid-run catalyst like Stavka or ZATO City Grid. It's worth saying that all of these cards only fire when rezzed "during a run on this server" which is important because it means you cannot use Ping to give the Runner a tag on your turn for End of the Line nor can you install Hafrún on a different server to the one the Runner is currently running on and expect it's ability to fire.

For the uninitiated, the Stavka + Hafrún combo involves using Stavka to rez a Hafrún just as the runner approaches the Stavka, allowing you to disable their Killer and attempt to forcibly fire the two program trashing subroutines. This can be beaten by having multiple Killers installed, flickering a Killer using Simulchip or bypassing the ice using something like Malandragem, Laser Pointer or Physarum Entangler. Or by having otherforms of redundancy, such as a pre-installed Boomerang or Botulus in addition to a Killer. Or, by simply destroying the ice on encounter using Arruaceiras Crew.

Fodder

Ob's ability to tutor an ice when needed and then dispense with it once it's outlived its usefulness while cascading into another card allows it to get value from ice other decks deem too unreliable. Ice like Envelopment or Sandstone are over efficient when rezzed but decline in efficiency over time, in the long term this isn't worth it for most Weyland decks but for Ob they can make the most of it during the honeymoon phase and then trash them using a catalyst once it starts to decline.

Furthermore, the many incidental purges that come from cards like Mavirus or Flyswatter can unintentionally refresh Sandstone, extending its usefulness.

Other ice that doesn't innate benefit from Ob but often shows up in Ob includes Maskirovka, Afshar or Kessleroid because they're reasonably efficient in their own right and because they can be tutored quite easily, or trashed by a catalyst to find another ice as needed.

Because Envelopment is 5-cost, many Obs deck that include it also like to include some 4-cost targets such as Syailendra or Tree Line but this isn't essential.

The Anatomy of a Turn

Most of the time, turns pass by rather intuitively, but when it comes to a strict "once per turn" ability such as Ob, it pays to understand the minutiae of turn structure. Importantly, start of turn triggers are said to exist before the turn proper, so if you fire Ob while using start of turn triggers such as Anthill Excavation Contract then you can still fire Ob an additional time during your action phase.

So for example, imagine an Anthill empties during your start of turn, you could then fetch a Cybersand Harvester during your start of turn window (before your mandatory draw), and then once your action phase begins, you can use the Cybersand to clicklessly install a Humanoid Resources and then use the Humanoid as you still have three clicks remaining. However, in this scenario, you would not be able to install a Spin Doctor off of the Humanoid trash since that would be the second trash of the turn.

However, if you imagine a situation in which you have already used Ob on the Runners turn, for example, using a Mavirus to install a Manegarm Skunkworks during a run, then an Anthill that trashes itself during your start of turn triggers would not fire Ob.

Another small detail unrelated to timing, is that you can use Obs ability purely for the shuffle. You can fire Ob when you trash a 0-cost card (like Mitra, just to forcibly shuffle your deck. You can't actually install a -1 cost card, since such a thing doesn't exist, but forcibly shuffling your deck could be important for breaking R&D lock or outmaneuvering Cataloguer, so it's something worth keeping in mind if there was nothing serious you actually wanted to search for that turn.

M.A.D. Combo Kill

Shoutout to Toron for reminding me that this monstrosity still exists in standard.

There are 2 main combo kill lines in standard for killing a Runner using Mutually Assured Destruction in Ob.

1. Play Nanomanagement -> play M.A.D. trashing at least one 4-cost card to tutor a Bass CH1R180G4 with Ob -> Click Bass CH1R180G4 -> play End of the Line -> play End of the Line

2. Play Nanomanagement -> play M.A.D. trashing at least one 3-cost card to tutor a Wage Workers with Ob -> play End of the Line gaining a click from having played 3 Operations this turn -> play End of the Line

Both of these are 4 card combos that require you to spend a lot of time setting up and pretty much exclusively build your deck around them and they are not very viable in Standard right now for those very reasons.

Fun Fact: The Eternal variant of this combo which involves M.A.D., Jeeves Model Bioroids and High-Profile Target is far quicker, more reliable and deadlier but thankfully we don't have to deal with that in Standard.

Wrap Up

This has been a fun excercise for me and hopefully this will be a useful resource for you dear reader. If I get the chance, I'll hopefully update this with new info when the next set releases. Assuming Ob is still around terrorizing Runners...

Umbrella is a cool card but having now existed for a few years, it doesn't seem to be that strong.

It doesn't typically find a home in anarch decks, even though you might think it could. Anarchs that install Botulus usually use Botulus to break the ice, and Umbrella would be superfluous. If the Botulus can't fully break the ice, you could play Poison Vial instead which has a lot of extra utility, against bioroids like Bran 1.0 for example. You might imagine that using Chisel with Umbrella is decent, but in practice I've never seen that work well.

Umbrella really only makes sense in Arissana Rocha Nahu: Street Artist decks, because for other runners it can be very clunky to get all the trojans in the right place to use umbrella to break ice and make a successful run.

As of Elevation release, many players are cold on Arissana Rocha Nahu: Street Artist because Madani might arguably just be better, having fewer restrictions and being usable on the corp's turn as well.

However, I think the main reason that Umbrella is weak is because of the text:

If at least one subroutine was broken this way, each player may draw a card.

On the face of it, one might think this is equally beneficial to the runner and the corp. However, I think actually, letting the corp draw a card on the runner's turn is more beneficial for the corp than the runner.

• If the runner is running HQ and this happens, it may dilute agendas held in hand and help protect the corp if the runner does access HQ.
• Many corp cards now require the corp to trash a card. So for example, using Umbrella to break one ice may provide fuel for cards like Anoetic Void or Boto
• It's generally harder for corps to draw cards than runners, especially with the rotation of Rashida Jaheem. Runners generally have lots of draw engines like Diesel, Dr. Nuka Vrolyck, The Class Act, Verbal Plasticity, which are played in many decks. Runners usually try to get more than one card drawn per click. Corps typically don't or can't do this nowadays -- there is Predictive Planogram but it's more often used for credits than draw. Red level clearance exists but isn't widely played. There are not too many assets that draw cards either.

Some corps like AU Co.: The Gold Standard in Clones and The Zwicky Group: Invisible Hands have built-in draw and then perhaps this argument doesn't apply. But typically, when I'm playing as a corp and the runner breaks something with Umbrella, my position in the game is improved by both me and the runner drawing a card during a run.

It may be as simple as:

If the runner draws a card with Umbrella, they are already running. And so even if the card is good, they probably can't play it right now, and don't have the benefit of planning their turn around this card. They might only have one click after this run ends, and this new card probably won't have impact until the runner's next turn. On the other hand, as the corp, when I draw on the runners turn I will start my next turn with extra cards -- starting with 6 cards is likely to lead to me having a much better and more impactful turn than I would otherwise. And the impact of this draw is likely going to happen for the corp before it happens for the runner.

It's not easy to measure, but having played enough games against players that use Umbrella, I find that it "brings me joy" as the corp to see the runner install Umbrella, and when they break something and we both draw a card, it usually feels to me like I'm getting a significant advantage. Make of that what you will.

Maskirovka stocks are way up now that Cleaver's banned! 3-4 to break for popular fracters, and only costs 1 on the face-check! If you want to go faaast but your agendas behind Maskirovka. Do this turn 1! In one minute, draw a maze that takes two minutes to solve!!!!

Right now, the only other review of this card is almost 5 years old.
In the meantime, the fourth, fifth, sixth and seventh rotation happened.
Belonging to Downfall, Divested Trust is now among the oldest cards in the whole standard format.
After more than 6 years in the active cardpool this agenda has seen … not much actually.

Let's revisit Divested Trust in the light of what's basically a different game now than 6 years ago.
Let's revisit Divested Trust in the light of Elevation and, more specifically, BANGUN: When Disaster Strikes.

I wrote a silly story of me using it in the form of a decklist, but for the sake of an actual review I'll go more into the mechanics.  

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Scoring  a 3/1 is always a pain.
You have the same effort as scoring a solid 3/2 agenda, but you only get 1 point and in the special case of this one you don't even get to keep that point, since the whole point of  Divested Trust is to be forfeited.
And not in a good way (like the newest agenda that wants to be forfeited) that enables other cards. No, Divested Trust's sole purpose lies in an ability that requires forfeiting itself as a cost.

This is a lot to ask. The fact that the pace of the game generally is faster now than it was when Divested Trust was made actually makes this even more of a burden.

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But it gets worse:
Divested Trust wants to be scored early, so that it can still be used when the runner steals an agenda without immediately winning the game. 
This makes it hard to use in any environment where the runner can get to 4 points reasonably fast. 
Bad news, that's the only environment we have. Corps can't really have a safe early game against the modern arsenal of early aggression tools on the runner side.

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And there's another downside: 
Divested Trust wants to be scored early, but without really doing that much to help the corp to develop.
Other 3/1s either accelerate the game instantly or continue to provide some sort of meaningful protection. 
Divested Trust does both once at some future point in the game barely under your control as a corp player.

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The one silver lining for this card is that it's super fun (for the corp) and swingy when it actually does "un-steal" (a very rare mechanic) 2 or 3 points the runner fought hard for, while simultaneously re-funding a corp that has spent a lot to defend these points. 
These moments are the reason I like the design concept, even if the card isn't objectively good.

Conclusion

In their early days of keeping this game alive NSG erred on the side of caution with this cool and unique agenda.
It's not good.
You should play it more often.

Hint: If you use top ability, remove Hannah and then bring it back with Privileged Access (or any other recursion ability) you may use the top ability again in the same turn - it's treated as a new card.