Stealing Game Mechanics - Blades In The Dark Flashbacks

[Sparky McDibben]

Hey, so for those of you who don't know, Blades in the Dark has a really cool little option whereby a player, in the middle of a heist, can trigger a flashback to set up an advantage or mitigate a disadvantage. I'd like to try these in 5E, but I need some help.*

I'm going to be running an urban campaign soon that will feature a premium on infiltration, intrigue, and general roguish shenanigans. Having a tool like Blades in the Dark's Scores will be supremely useful, and most of it maps fairly well onto 5E. The only thing that is giving me a problem are flashbacks.

My problem here is that 5E is really bad with costs - almost everything is a binary pass/fail. Here's what it costs a BitD character to do a flashback:


Stress, which is sort of like mental hp (not exactly, but closest analogue I can come up with)
Risk of failure (may involve a roll)
Cannot undo previously established elements

That last one might be a little vague, so let me quote John Harper himself here: "For instance, if Inspector Helker confronts you about recent thefts of occult artifacts when you’re at Lady Bowmore’s party, you can’t call for a flashback to assassinate the Inspector the night before. She’s here now, questioning you—that’s established in the fiction. You can call for a flashback to show that you intentionally tipped off the inspector so she would confront you at the party—so you could use that opportunity to impress Lady Bowmore with your aplomb and daring."

What could I charge a PC to perform a flashback in 5E? There's no obvious analogue to Stress in 5E. The most obvious option is a level of exhaustion or 1d6 Hit Dice, but that level of exhaustion is steep in a skill-heavy game - you're basically saying they don't get to contribute for the rest of the Score. That's because they'll be at disadvantage for all ability checks, and that player's going to be very reluctant to participate because they're more likely to fail.

Anybody have some thoughts on this? Have you ported other BitD mechanics into your 5E games? How did it go?

*I swear to God, if your answer to this question is "Just play Blades in the Dark," I will hunt you across the multiverse. I will find you. I will walk in the door of your demiplane, and I will whisper a ton of compliments in your ear as I frenziedly scribble "MY PLAYERS ONLY PLAY 5E!!!!!" on walls. In Sharpie.

[Thunderous Mojo]

Spending Inspiration could be the cost.

If Inspiration is too light of a cost, consider giving Narrative points that can be used for this purpose.

The question is how frequently do you want people to use the mechanic.

I myself like it when a player spends a Narrative point/Inspiration to make an NPC a relative, or someone they know.

[Unoriginal]

Spending Inspiration could be the cost.

If Inspiration is too light of a cost, consider giving Narrative points that can be used for this purpose.

The question is how frequently do you want people to use the mechanic.

I myself like it when a player spends a Narrative point/Inspiration to make an NPC a relative, or someone they know.

Those seems like appropriate costs indeed.

The DM could award Narrative Points for RP scenes, great ideas and anything that would usually get the PC Inspiration, too.

[Sparky McDibben]

Spending Inspiration could be the cost.

If Inspiration is too light of a cost, consider giving Narrative points that can be used for this purpose.

The question is how frequently do you want people to use the mechanic.

I myself like it when a player spends a Narrative point/Inspiration to make an NPC a relative, or someone they know.

My problem with this is that it's like charging someone $5 and then handing them $20 to pay for it. I'm charging them a resource I'm in charge of distributing, instead of one that's linked to their character.

[solidork]

I was going to suggest Inspiration, combined with being more explicit with how you award it. I talk about the system my group is using in this thread:

https://forums.giantitp.com/showthread.php?648061-Beats-in-5e-Gamifying-Inspiration&p=25661814#post25661814

TLDR; you come up with inspiration triggers based on your personality, ideals, bonds, flaws or something else important to your character. Pick three of those each session, and when you satisfy them you immediately get inspiration. We've been doing it where you have to switch out the beats when you trigger them for at least a session.

[Frogreaver]

Hey, so for those of you who don't know, Blades in the Dark has a really cool little option whereby a player, in the middle of a heist, can trigger a flashback to set up an advantage or mitigate a disadvantage. I'd like to try these in 5E, but I need some help.*

I'm going to be running an urban campaign soon that will feature a premium on infiltration, intrigue, and general roguish shenanigans. Having a tool like Blades in the Dark's Scores will be supremely useful, and most of it maps fairly well onto 5E. The only thing that is giving me a problem are flashbacks.

My problem here is that 5E is really bad with costs - almost everything is a binary pass/fail. Here's what it costs a BitD character to do a flashback:


Stress, which is sort of like mental hp (not exactly, but closest analogue I can come up with)
Risk of failure (may involve a roll)
Cannot undo previously established elements

That last one might be a little vague, so let me quote John Harper himself here: "For instance, if Inspector Helker confronts you about recent thefts of occult artifacts when you’re at Lady Bowmore’s party, you can’t call for a flashback to assassinate the Inspector the night before. She’s here now, questioning you—that’s established in the fiction. You can call for a flashback to show that you intentionally tipped off the inspector so she would confront you at the party—so you could use that opportunity to impress Lady Bowmore with your aplomb and daring."

What could I charge a PC to perform a flashback in 5E? There's no obvious analogue to Stress in 5E. The most obvious option is a level of exhaustion or 1d6 Hit Dice, but that level of exhaustion is steep in a skill-heavy game - you're basically saying they don't get to contribute for the rest of the Score. That's because they'll be at disadvantage for all ability checks, and that player's going to be very reluctant to participate because they're more likely to fail.

Anybody have some thoughts on this? Have you ported other BitD mechanics into your 5E games? How did it go?

*I swear to God, if your answer to this question is "Just play Blades in the Dark," I will hunt you across the multiverse. I will find you. I will walk in the door of your demiplane, and I will whisper a ton of compliments in your ear as I frenziedly scribble "MY PLAYERS ONLY PLAY 5E!!!!!" on walls. In Sharpie.

Seems to me a flashback could cost hit dice.

All this said - getting your players on board doing a score instead of more free form playing will be your pain point. I struggle to get my 5e in players to actually do a score in a blades game instead of trying to proactively set up the position in their favor. Soooo good luck with that.

[Atranen]

I've done this; I gave them a limited number for the score, and it worked well. 2 flashbacks worked well for me.


My problem with this is that it's like charging someone $5 and then handing them $20 to pay for it. I'm charging them a resource I'm in charge of distributing, instead of one that's linked to their character.

I think it's ok; in a certain sense, the GM controls HD, spell slots, Hps, etc. The resource is just linked to the group rather than a particular character.

[BeholderEyeDr]

I've run or played in a few heists in 5E that tried some kind of flashback system, and they've actually never worked--in several cases, they were never used! The main reason why is that most of our fun in D&D comes from when things go wrong: we would rather play through that and deal with these moments of crisis, rather than use a mechanic to avoid it. For us, flashbacks were actively unfun when used, and tended to never be used as a result. We would rather improvise and problem solve within the active situation, rather than flashback to retroactively declare some bit of planning. This may just be my groups, and your group may be totally different: but I actually have a sneaking suspicion (pun intended) that it may be true somewhat generally. I'd think hard whether the value of this mechanic is worth the cost of adding it, especially compared to doing something much simpler like saying, "if you want to, you can use inspiration to reroll a failure, and if you do so you can justify it by flashing back to some kind of preparation you did earlier." Then you can have a 'heist prep' phase beforehand where they can accumulate inspiration in addition to the other narrative benefits they might gain. But this can all handled by you behind the scenes, your players don't really see a different between 'heist mode' and normal adventuring.

On the other hand, something I've used to great effect in moments of tension or subtlety is some kind of 'warning system' of increased consequences. This is probably something obvious that lots of people do, but I'm going to spell it out here anyway. Essentially, the encounter/scene is built as a skill challenge, but failures change the situation to make things more difficult for the PCs: the castle guards become more vigilant, more guards are called on duty, doors are locked, targets of importance are moved to secure locations, the evil ritual begins, etc. This works for heists and espionage, obviously, but it can also be used for social/intrigue encounters: anytime you want failure to be meaningful, but you don't want a single failure to be able to completely derail an encounter. As above, I use it pretty informally rather than going into 'intrigue mode,' so to my players it just feels like normal play: but for me, the added structure is really helpful to crafting the mechanical stakes of an encounter/scene (just like normal skill challenges).

[Thunderous Mojo]

TLDR; you come up with inspiration triggers based on your personality, ideals, bonds, flaws or something else important to your character. Pick three of those each session, and when you satisfy them you immediately get inspiration. We've been doing it where you have to switch out the beats when you trigger them for at least a session.

I run something on a similar principle, which is largely based off Cypher System rules, and the rules have worked well for me.

I essentially:
Let the player set his character arc goals, and what success would look like. Let the player decide how many milestones are in their character arc.
Each milestone is worth one point.
Completion of the arc, yields points equal to the milestones.

[Tanarii]

Just play Blad.... *reads end of post*

Uh, I mean ...

The obvious thing would be to introduce Stress. And the mechanics for working it off.

One thing I'd recommend is either making it harder for some classes to work off stress, or have them pay more stress up front. Because an intrigue heavy campaign is likely to strongly favor some classes otherwise.

In other words, give Fighters and Barbarians a boost in flashbacks as a class feature.

[Unoriginal]

My problem with this is that it's like charging someone $5 and then handing them $20 to pay for it. I'm charging them a resource I'm in charge of distributing, instead of one that's linked to their character.

You're always charging PCs ressources you'te in charge of distributing, though.

But fair, let's think differently.

How about giving the group a certain number of Downtime Points (ex: one per PC+1) and the player has to spend one if they want to:

-Do a Downtime activity

-Recover health during a Long Rest

-Do a Flashback

That way there are real consequences, and it's something the group can manage together.

[Thunderous Mojo]

In other words, give Fighters and Barbarians a boost in flashbacks as a class feature.

I hate this idea. The players of Fighters and Barbarians are just as capable of clever play as the players of other classes. (Indeed, many people play all sorts of characters).

The 2001 remake of Ocean’s Eleven has a scene in which an overly strong handshake, is sufficiently intimidating to garner a discount when purchasing used vans for the heist.

5e has rules that cover using different ability scores for checks.

I have seen a Vhuman Barbarian use the Actor feat, to bluff their way into a prison, and mimic guards voices to great effect. Clever players are clever, regardless of what class their current PC is.

Subsystems that, on the surface should be class neutral, should probably remain neutral, for fairness.

[Sparky McDibben]

Seems to me a flashback could cost hit dice.

All this said - getting your players on board doing a score instead of more free form playing will be your pain point. I struggle to get my 5e in players to actually do a score in a blades game instead of trying to proactively set up the position in their favor. Soooo good luck with that.

Both of these points interest me, as they highlight the both the tendency of 5E play culture and remind of the Uncharted Journeys system, which I think I could leverage for this instead of BitD.


I've run or played in a few heists in 5E that tried some kind of flashback system, and they've actually never worked--in several cases, they were never used! The main reason why is that most of our fun in D&D comes from when things go wrong: we would rather play through that and deal with these moments of crisis, rather than use a mechanic to avoid it. For us, flashbacks were actively unfun when used, and tended to never be used as a result. We would rather improvise and problem solve within the active situation, rather than flashback to retroactively declare some bit of planning. This may just be my groups, and your group may be totally different: but I actually have a sneaking suspicion (pun intended) that it may be true somewhat generally. I'd think hard whether the value of this mechanic is worth the cost of adding it, especially compared to doing something much simpler like saying, "if you want to, you can use inspiration to reroll a failure, and if you do so you can justify it by flashing back to some kind of preparation you did earlier." Then you can have a 'heist prep' phase beforehand where they can accumulate inspiration in addition to the other narrative benefits they might gain. But this can all handled by you behind the scenes, your players don't really see a different between 'heist mode' and normal adventuring.

That is a surprisingly deep thought to hit me with on Tuesday morning, Doc. It actually sent me all the way back to the Alexandrian, here. (https://thealexandrian.net/wordpress/44891/roleplaying-games/gm-dont-list-11-description-on-demand) Because I think you've hit on something that's really interesting - Blades occupies this weird fuzzy ground between role-playing and story-telling games, where the PCs can use metacurrency (Stress) to drop in changes to a scene (a pretty classic element of STGs).

And you know what? You're right. This gives the PCs control of the environment at the cost of their control over their characters. Because in Blades in the Dark, it's intended to let the player recover from a bad die roll and avoid a bunch of interminable planning. I recently read this article at the Guardian (https://www.theguardian.com/games/2022/dec/13/first-time-as-a-d-and-d-dungeon-master-dungeons-and-dragons) where the journalist described running 5E as "like trying to play The Witcher 3 with the Oxford University debating team." And that is part of the fun - trying to set things up in your favor. It just normally takes so darned long for the PCs to do so!

However, I was also thinking about where else I've seen abstraction employed to good effect. I think this is a similar situation to overland travel - you can get into very long debates over "how many oxen do we need to bring?" And so I wonder if the solution might not be to leverage Uncharted Journeys by Cubicle 7. I've got the kernel of an idea brewing in the back of my head right now.


Just play Blad.... *reads end of post*

Uh, I mean ...

The obvious thing would be to introduce Stress. And the mechanics for working it off.

One thing I'd recommend is either making it harder for some classes to work off stress, or have them pay more stress up front. Because an intrigue heavy campaign is likely to strongly favor some classes otherwise.

In other words, give Fighters and Barbarians a boost in flashbacks as a class feature.

You got a chuckle out me!

That is a spicy meatball of a take, good sir. Don't get me wrong, I love it, but in BitD, the main purpose of Stress is to avoid harm (you can take Stress to just avoid an effect, for anyone unfamiliar with the system). 5E players already have so many ways to avoid consequences (including the Lucky feat, which I know one of them is taking). But if I take this and combine it with Unoriginal's advice below, I can start putting Miracle-Gro on that kernel of an idea I mentioned.


You're always charging PCs ressources you'te in charge of distributing, though.

But fair, let's think differently.

How about giving the group a certain number of Downtime Points (ex: one per PC+1) and the player has to spend one if they want to:

-Do a Downtime activity

-Recover health during a Long Rest

-Do a Flashback

That way there are real consequences, and it's something the group can manage together.

This is interesting; I want to come back to these ideas.

OK, I think you guys are talking me out of this idea. And you're all mostly right. I don't see a good way to integrate Flashbacks into a clean heist structure that has the players focused on their characters instead of the world.

But I think y'all have brought up a bunch of kickas$ points, and I want to price in a lot of this feedback using a different mechanical structure: Journeys from Uncharted Journeys. (https://forums.giantitp.com/showthread.php?652224-Uncharted-Journeys-Third-Party-5E)

For those of you unfamiliar with that product, each Journey is basically a skill challenge. The PCs set the destination, and undertake preparations. The DM picks two numbers - the number of Encounters you want the party to have, and the base DC of those challenges. Then, you randomly determine which encounters they have, and they play through (with compounding consequences) those encounters.

So here's what I'm thinking for a starting procedure:

PCs pick a target and an approach (the method they'll be gaining access with, which might be social, stealth, magical, etc.)
DM determines the base DC of all skills to be used in the heist, and how heavy the security is (which sets the number of complications)
Each PC prepares for the Heist (makes diversionary items, recons the target, bribes a guard, etc)
DM determines the complications for the heist (the current owners are selling the heist target right now, the guards are doing their walkthrough early, etc.)
PCs play through these complications as circumstances compound, eventually either achieving their goal, running away, or slaughtering everyone and laughing amidst the ashes of their carnage
If the PCs achieve their goal, they make a Getaway roll, which determines how "cleanly" they escape

DCs run from 15 (for moderate-difficulty heists) to 25 (for epic thefts). Security complications run from 1 - 5, and there's a 5-slice Alarm Clock in play. Each failure during a complication ticks a box on that Alarm Clock, raising the DC by 1 per tick to a max of 30. Critical failures add 2, but Once the Clock is full, the security is actively aware that someone is here, and call for reinforcements, cops, or both, depending on the circumstances (adding a complication to the getaway).

PCs can invoke Stress, which adds +1d8 to a single roll per point of Stress incurred by the player. Stress maxes out at 5 per player character, and if you have as much or more Stress than your Wisdom modifier, you have disadvantage to Wisdom saving throws.

The Getaway roll is [1d12 + succeeded complications]. The higher the roll, the cleaner the Getaway. A roll of 1 - 3 might mean the cops / reinforcements are right on your heels, while 4 - 6 means no one is following you right yet, but you know you're on someone's radar. And so on.

In downtime, the PCs get paid (provisionally), they clean up loose ends, do downtime activities or burn off Stress. Note the "or" - each character has to choose what they want to do. Stress is burned off by the player telling the DM how they want to blow off steam, typically an indulgence of some kind. At the end of each week of downtime, each player burning off Stress is charged 1d100 gp. If you run out of cash, you are now in debt to someone of the DM's choice. When you would burn off your last point of stress, make a Wisdom saving throw vs DC 15. If you fail, you overindulge. The Stress still gets burned off, but you've been indiscreet in some way - bragging about your antics, for example, or go on a bender and disappear for 1d4 weeks, or piss off someone important.

I know there's a lot of work to do to flesh this out, but I think that's a good skeleton. I'm open to critique and analysis. If you've got questions, by all means ask. Thanks for steering me out of troubled waters, y'all!

[Unoriginal]

This is interesting; I want to come back to these ideas.

OK, I think you guys are talking me out of this idea. And you're all mostly right. I don't see a good way to integrate Flashbacks into a clean heist structure that has the players focused on their characters instead of the world.

But I think y'all have brought up a bunch of kickas$ points, and I want to price in a lot of this feedback using a different mechanical structure: Journeys from Uncharted Journeys. (https://forums.giantitp.com/showthread.php?652224-Uncharted-Journeys-Third-Party-5E)

For those of you unfamiliar with that product, each Journey is basically a skill challenge. The PCs set the destination, and undertake preparations. The DM picks two numbers - the number of Encounters you want the party to have, and the base DC of those challenges. Then, you randomly determine which encounters they have, and they play through (with compounding consequences) those encounters.

So here's what I'm thinking for a starting procedure:

PCs pick a target and an approach (the method they'll be gaining access with, which might be social, stealth, magical, etc.)
DM determines the base DC of all skills to be used in the heist, and how heavy the security is (which sets the number of complications)
Each PC prepares for the Heist (makes diversionary items, recons the target, bribes a guard, etc)
DM determines the complications for the heist (the current owners are selling the heist target right now, the guards are doing their walkthrough early, etc.)
PCs play through these complications as circumstances compound, eventually either achieving their goal, running away, or slaughtering everyone and laughing amidst the ashes of their carnage
If the PCs achieve their goal, they make a Getaway roll, which determines how "cleanly" they escape

DCs run from 15 (for moderate-difficulty heists) to 25 (for epic thefts). Security complications run from 1 - 5, and there's a 5-slice Alarm Clock in play. Each failure during a complication ticks a box on that Alarm Clock, raising the DC by 1 per tick to a max of 30. Critical failures add 2, but Once the Clock is full, the security is actively aware that someone is here, and call for reinforcements, cops, or both, depending on the circumstances (adding a complication to the getaway).

PCs can invoke Stress, which adds +1d8 to a single roll per point of Stress incurred by the player. Stress maxes out at 5 per player character, and if you have as much or more Stress than your Wisdom modifier, you have disadvantage to Wisdom saving throws.

The Getaway roll is [1d12 + succeeded complications]. The higher the roll, the cleaner the Getaway. A roll of 1 - 3 might mean the cops / reinforcements are right on your heels, while 4 - 6 means no one is following you right yet, but you know you're on someone's radar. And so on.

In downtime, the PCs get paid (provisionally), they clean up loose ends, do downtime activities or burn off Stress. Note the "or" - each character has to choose what they want to do. Stress is burned off by the player telling the DM how they want to blow off steam, typically an indulgence of some kind. At the end of each week of downtime, each player burning off Stress is charged 1d100 gp. If you run out of cash, you are now in debt to someone of the DM's choice. When you would burn off your last point of stress, make a Wisdom saving throw vs DC 15. If you fail, you overindulge. The Stress still gets burned off, but you've been indiscreet in some way - bragging about your antics, for example, or go on a bender and disappear for 1d4 weeks, or piss off someone important.

I know there's a lot of work to do to flesh this out, but I think that's a good skeleton. I'm open to critique and analysis. If you've got questions, by all means ask. Thanks for steering me out of troubled waters, y'all!

If you are using the Uncharted Journey as a basis, I think you should go full "Sparky McDibben's Heist system" and create positions similar to the Uncharted Journey's ones for the PCs to take, such as the Sneak (who does the actual stealing/planting/spying during the heist), the Researcher (who finds the info needed for the heist to be carried), the Interventionist (who acts when things go wrong) and the Distraction (who is here to help the everyone not get caught).

Additionally, each "job" of the heist could have different potential fail results (ex: in Inception, when the Researcher didn't manage to find out their target has been trained to resist the mind manipulation, making the heist much more dangerous).

[Sparky McDibben]

If you are using the Uncharted Journey as a basis, I think you should go full "Sparky McDibben's Heist system" and create positions similar to the Uncharted Journey's ones for the PCs to take, such as the Sneak (who does the actual stealing/planting/spying during the heist), the Researcher (who finds the info needed for the heist to be carried), the Interventionist (who acts when things go wrong) and the Distraction (who is here to help the everyone not get caught).

Additionally, each "job" of the heist could have different potential fail results (ex: in Inception, when the Researcher didn't manage to find out their target has been trained to resist the mind manipulation, making the heist much more dangerous).

I really like that! I'm thinking Mastermind replaces Leader (can give each crew member advantage once per heist); Lookout replaces Sentry (can, once per Heist, create a diversion to reduce the difficulty of a complication); Cleaner replaces Quartermaster (can, once per Heist, choose to mitigate (but not nullify!) a consequence from a failed complication or group check); Recon replaces Outrider (can, once per Heist, override the DM's roll of a complication with a different complication).

As you can probably tell, I don't want to give the PCs more than one additional kind of resource to manage (and that's Stress). Rather, I want to give them a card to play, based on the archetype they're embodying. The other problem I have with Uncharted Journeys is that there's only four roles, and I have five players. So I want to add two more roles: the Occultist, and the Burglar. The Occultist is the person who tags along to handle any and all magical shenanigans. So they're more focused on disarming wards and preventing magical alarms from going off. The Burglar is focused on getting access to and retrieving the goods. So they're more focused on climbing over rooftops, rappelling down ropes, and picking pockets.

The trick, I think is in finding that balance so that any given class doesn't completely dominate a given role. Like, how do you prevent the party rogue from having to be the burglar all the time? Well, you design the group travel check such that it avoids Dex (Stealth), Dex (Sleight of Hand), and Dex (Acrobatics). You need to vary it up so that other classes can shine as the Burglar if they want. So instead, I'd probably need to focus on Strength (Athletics) for climbing / second-story work, Constitution (Stealth) to see how long you can hold a crazy stealth pose, and probably Dexterity (thieves' tools) to let the rogue shine if they want to.

And after all that, I'll need to update the various kinds of encounters they can have. Right now, I've got the following:


Incursion - Someone unexpected shows up, whether that's a surprise inspection of the security guards or another crew looking to the steal the target
Bonus: The PCs have the option to acquire additional loot, at the risk of garnering extra attention from the authorities
Obstacle: An unexpected trap or hazard is present (target is in a sealed glass case, for example)
Needs Assistance: There's someone present who needs help, whether that's a bunch of folks headed to a slave auction, or a night auditor having a heart attack.
Shift Change: The guards have changed their walkthrough times, and now they're closing on the PCs.
A Fantastic View: The PCs have a momentary glimpse of something beyond their quotidian concerns (a breathtaking view of the city, a sudden meteor shower visible overhead, a dragon wheeling far overhead, etc.) that either lift their spirits or remind them of how small they are.
Shakedown: The local criminals threaten to disrupt the Heist unless they get cut in.
Bolt-Hole: PCs discover a great hiding place or observation post (unless there's something wrong with it they didn't foresee).
Signs of Heists Past: The PCs discover signs of other thieves having broken into this area. They have the opportunity to find something helpful left behind by the previous crew, or to have a problem with weakened supports collapsing under them.
Cursed Goods: Either the target or the location is cursed, and the curse manifests now in front of the PCs, causing some serious spookiness and testing the PCs resolve.
WAAAAGH!: The Heist location comes under full-blown assault. That might be from a local criminal gang trying to overwhelm the security, or reinforcements have shown up to help the guards, or the cops arrived in response to a silent alarm.
Fateful Encounter: The PCs discover someone they did not expect, and have the opportunity to make an ally or an enemy.


It's not elegant (I'm basically just twisting Cubicle 7's work), but I think it'll get the job done. Thoughts?

[Unoriginal]

Rather than having an Occultist just to deal with the supernatural, I would have some kind of Expert whose job is to deal with any weirdness.

I don't think that having a "that's the caster's job" role would be a good thing, even if it's an indirect incentive.

[KorvinStarmast]

Seems to me a flashback could cost hit dice. That was my first thought. But using inspiration strikes me as the better idea since blades has other currency or cost (clocks, stress, trauma) built in that D&D 5e does not.
All this said - getting your players on board doing a score instead of more free form playing will be your pain point. I struggle to get my 5e in players to actually do a score in a blades game instead of trying to proactively set up the position in their favor. We are all working our way into a new mind set, but I take a lot of stress points to help the other players; thankfully, my vice episodes remove most of it, although I do have a trauma point already.

[Yakk]

Here goes...

Each PC has to have 2 Bonds. These Bonds must be aligned either Lawful, Chaotic, Evil or Good. The alignment of your bonds does not determine your PCs alignment, but they do determine the type of bond.

Good bonds are selfless bonds, things you would sacrifice for. A parent's bond for a child, or a cause you believe in and would self-sacrifice for.
Evil bonds are selfish bonds, thing you value because of benefit to you. Your employment with the South Seas trading company, or your social status as a Registered Diet Mage.
Lawful bonds connect to organizations and abstractions. Your loyalty to the Crown not King, or to a Church, would be Lawful.
Chaotic bonds connect to individuals. Your loyalty to the Queen not the Crown, or to a Prelate, or to your Brother, would all be Chaotic bonds.

If your bond is missing an alignment along one axis, your bond is also Neutral.

Bonds can have 1 element of each axis.

What can you do with Bonds:
Once per game session you can tap a bond for inspiration and roll 1d20, replacing the result of a roll. Inspiration replacement rolls ignore disadvantage/advantage, and are optional replacements (only use if better).

What kind of roll you can use a bond on is determined by its alignment. To pay for your tapping of a bond, the player must tell a short (~1 minute) story about a past event illustrating your characters connection to the bond.

Good bonds can be used to reroll attacks on your allies and saving throws your allies make.
Evil bonds can be used to reroll attacks you make, any number of damage dice on a roll by you.
Lawful bonds can be used to reroll attacks on you, or saving throws you make, or to negate forced movement of any kind on you for the turn.
Chaotic bonds can be used to reroll attacks or damage rolls by your allies, and lets you make an extra saving throw against an effect that you could make a saving throw once on your turn (regardless of if it requires an action to make the throw) or to escape a grapple.
Neutral bonds can be used to reroll saving throws foes make.

...

Then, for flashbacks, require the player to have a tapped a bond this session already. You put a 2nd checkmark when they do a flashback.

...

Ok, the design goals here.

1. The bonds attach the players to the world.
2. By forcing the player to narrate about their bond, other people at the table learn about it. So it isn't just a secret with the DM or in a backstory somewhere.
3. The Player is in charge of tapping their bond. It is a free reroll 1/session, so they have lots of incentive to use it.
4. They do not have to justify the bond is tied to the action they are rerolling, except via the bond's alignment. This makes it far more likely to be used.
5. The alignment connections on the bond are a bit of flavour. Players can decide what kind of attachments the character has with the world, and it has a slight mechanical impact.
6. Flashbacks don't need to make the character worse, they just need to be rationed.
7. Gating Flashbacks behind bonds/inspiration use means you'll be looking to use inspiration to unlock flashbacks instead of saving inspiration, or you'll use inspiration in a scene, have it fail, then use a flashback immediately.