Hi this is my first time creating a campaign for my friends. I am wondering how to start it off with my players in an Amnesia state, without growing suspicion that the BBEG tricks them? Or even how to work around it so that my player's would still have fun learning the backstories unfold without showing the BBEG early on. I want to work this out with my player's but I am having a hard time thinking as how to let them create their own player's backstories without the sense that they are being tricked or having memory loss. Let's say they would have a dead loved one in their backstory, but as the campaign starts they would seemingly continue to communicate with the loved one as if they are alive. I am still creating this so I haven't had session 0 with the group yet. But the tone of this campaign is purely focuses around on redemption, teamwork to go through griefance , and fun moments here and there.

CONTEXT: 

The players would be starting off In a large group of people (lets say a small village amount), who they assumed to be living and traveling with. How each of the player's origin of meeting each other has been a blurry memory. All they know is that they are traveling with the group of people that consists of each of their loved ones, village folk, and the other players. To set off the tone, the players would be caught off in the act of the village folk would deem as a sin (yes this is planned by the elders). Due to this serious act, the village elders would cut off the whole party from them, yet keep their loved ones still since they all swore a powerful oath to not cause betrayal or harm within the villagefolk. This does not go well or our heroes since they cannot allow to be separated from their loved ones again. 

The village elders and council would agree that in order for them to be led back at this village community, they would have to do 12 labors and collect trophies as of proof to the elders. (Yes this campaign has a huge reference to the 12 labors of Heracles, and obviously will be catered within DnD)  Whilst our heroes are in the process of these adventures, they'll be able to gain trust within each other and regain parts of their pasts. This format would be a good start for a long term session, for each labor would be 1 session.

THE PLOT:

Once they have collected all proof of each labor, the story shifts. The elders, the council, the whole village are not who they say they are, they are but a cult, serving under a sleeping beast. (I am still in the process of assigning DnD related monsters that fit within the labors and the bbeg). The trophies are the recipes they need to fully break the cage and fully summon the beast they are trying to awaken. (A bit of reference from IT Welcome to Derry as well for the whole keeping the beast caged in thing)  The loved ones that seemingly faithful to stay within the village, are nothing but changellings that take the faces of the people they've lost. And because of the shift and clues the heroes acquired, Memories come flooding back in, realizing as to why they ended up with "the cult". Nothing but heroes that seek past glories, lost love and pasts they run away from, the cult found them as victims to do their bidding.And around this time, the players would have enough levels to battle, or work their way through the BBEG. 

Anyways I appreciate the time if ya'll reached this far. Hope y'all have a good day :D

The best advice I can give: Do not do this and find a new way to start your campaign.  This kind of start is almost exclusively bad for both players and yourself long term.

Starting with why this is bad for players, a player’s backstory is one of the few places they get to be in the driving seat during an entire campaign.  While the backstory is, of course, subject to DM approval and a dialogue about making it work within the campaign world, it is still a decision players take the initiative on, with the DM being the one responding to the decisions of the players.

Amnesia takes that initiative away from players and puts it back in the DMs hands, with the DM having to either hand wave away some of the amnesia elements to imposing their will upon this element of player agency, creating the very problems that you mention in your post… as well as a general air from the very start of the campaign that you are the kind of DM who will steamroll player agency for the sake of your own narrative.

For your own difficulty, backstories provide the DM a roadmap of “here is what I, as a player, care about. They provide valuable information that you can use throughout the campaign to create tension, make players feel heard, and make players feel they had a hand in creating the world and plot.  A forced amnesia plot sort of overwrites all that - even if they wrote their own backstory and later had the amnesia imposed, they still taints their backstory in a way that can shift their player perspectives and interests.  Moreover, as mentioned above, this creates a negative impression for players of your priorities as a DM, which can make it harder for them to trust you moving forward, and thus make it harder for you to ask them to trust you when the need arises.

The most you should ever do is “you do not know how you go to this specific place” (a pretty standard start) not the kind of “you forgot things important to your character” amnesia you propose here. 

I would also say, stying your entire campaign around going though loss and grief (what I presume you mean by “griefance” based on context) is a very, very, very dangerous thing to do as a DM.  You run the risk of making a campaign that hits far too close to home for your players, many of whom might have strong experiences with grief.  This is the kind of thing where the DM might think they are doing something profound and optimistic, but really could be making a fairly bleak environment that can be insensitive to others’ trauma.  That doesn’t mean that cannot be pulled off - but it needs to be pulled off by a DM who is capable and sensitive of those concerns.  I think you really need to think about that and ask yourself candidly if that is something you think you can handle respectfully. 

I see I see, I didn't think of it that way. I guess I was struggling to bring out a good story for my friends since they generally love the idea for plot twists. I fear that it'll be too bland for my friends or I won't know what to do mid campaign. I appreciate the advice and tips, if it's alright to ask how do you manage homebrew or just prep in general?

For the most part, as long as you are hanging out, playing with friends, and not falling into any of the DM mistakes that make the game miserable (not thinking about your players, putting a desire to tell "your" story over a collaborative story, being unfair, etc.), that is all you really need to have fun in a campaign.  Yes, it can be more fun if you have a DM with a grand plan and complex characters and design, but this is your first campaign.  It will be messy, you will make mistakes, and, unless your friends are jerks, they will forgive you for some of those first-time glitches every DM has.  So, I would not stress out too much about the game being "too bland for [your] friends".

Now, regarding your questions, there are lots of different ways to prep for a campaign - both in terms of how you create a homebrew world and how you craft a campaign overall.  Every person is going to be different in terms of what works for them, and there will be trial and error as you figure out what works for you.  By the end of your first campaign, you will certainly think "I should have done X differently from the start" - I know I still think that, and I have run multiple campaigns to level 20+ over the years.  

Still, there are a couple general things I would keep in mind as you craft your world.

1.  Plot twists are fun - too many plot twists are not.  What makes a plot twist exciting is the emotional impact when it hits--that moment where your expectations are subverted and something changes.  That the person you thought was evil turns out to be working toward the same end as you.  That the person you thought was good secretly was against you.  Those kinds of moments make for memorable campaign story beats - if you do not use them too often.  Once you start using them all the time, they do not stand out as much and players start to predict their happening.  

You want to think of your plot twists well in advance so you can subtly drop clues.  If Captain Bob is going to be evil, you should know that from the start - so you can do things like have Captain Bob show up just a little too late to stop a problem; have the bad guys seem to undermine a plan the players told to Captain Bob.  Little things that might be innocent, but, in retrospect, make your players go "ohhh, that all makes sense." 

Plot twists also can be rapid ones (ex. spending an entire session trying to help someone and have the reveal at end of session, so it hits hard because the players are still emotionally invested in their victory of helping) or playing the long game (build a relationship slowly over several sessions or longer, so the players are really stung by the betrayal).   Both have their place and do slightly different things, so think through what works for a given moment.  

2. You should have a general campaign idea from the start.  Figure out who your big bad is and work back from there.  What would their motivations be?  What drives them?  How would they accomplish those goals?  What stages would they follow for those goals?  That helps you plan out various levels of play for your expected campaign length, as well as lets you react to player decisions because you have a character you know, understand, and can then think about how that character would react to the changing circumstances created by players. Remember, even if you sketch out an entire campaign, you have to remain willing to change the campaign based on how the players change the world - your campaign outline is just an outline, not a script.  When working on your outline, also do not just think of the BBEG - add some generals and major helpful NPCs to the concept, so you have a bit more fleshed out than the single bad guy. 

3. Do the amount of prep that makes you feel comfortable.  You do not have to make an entire homebrew world or campaign from scratch right at the start of the campaign.  The immediate area the players are in and an outline of the campaign are really all you need to prep.  Sure, you can obsessively make pages upon pages of NPCs, worldbuilding lore, world maps, etc. (which is what I do), but that is a lot of work that you frontload when you do not need to.  If that amount of work is intimidating, you can always just create new things as you go along, staying a step or two ahead of the players instead of dozens. 

4. Remember, this is a game and you should have fun.  Many DMs get so caught up in the work that they forget this is supposed to be enjoyable for them as well.  Fun can be infectious, so if you are having fun playing something you enjoyed creating, your players likely will pick up on that and have fun as well. 

Amnesia can work but adding it as means to hoodwink the PCs feels a little unpleasant.

I have done something similar to what you are proposing, but I didn't do them together.
The Amnesia was for a bunch of Theater friends, and it was expressed by them not knowing anything, but then certain objects would trigger memories and i would say " What memory do you have related to this object" and they would get to make up their backstories on the spot.

The "hoodwinked by a Cult" was more false memories than amnesia. During character creation I asked the question " How do you relate to Saint Serra the Blessed healer" who was the supposed pinnacle of this community. I also didn't take too many precautions against them solving the "mystery" and peppered in people who would say " I have never heard of her" and such things that would reasonably lead people to the fact that "Saint Serra" didn't exist. The players then could by their actions try and figure out their real memories or why they would have them memories.

They were part of the play and not a " Haha! i hoodwinked you into working for the bad guy!" in both cases It wasn't a trick to railroad, it was either a chance to improv, or a knot for them to untie. And i tailored both of these to the players because i knew beforehand they would be into either Improv story crafting or mystery solving. 

If you are going to try this, give the players the freedom to see past the trick. It returns agency to the players.

Caerwyn has some great advice, I’ll just add a little. 

On amnesia, what if one of the PCs dies, or the player moves away and you need a new player or something? How do you add in another character who also has this amnesia? That’s often the Achilles heel for high-concept campaign ideas is what if you need a new character in the mix.

As for making your own campaign, I’d say start small. PCs are in a town, there’s a dungeon over that way and some bandits over that way and the big city is back that way. Sometimes, that can be enough. While an idea of who the BBEG is and what they are doing can help, you can also start with no big ideas, and let things evolve. The PCs go to fight the bandits, one escapes and holds a grudge. Maybe that person becomes a kind of mini-boss opposing them until level 4-5ish. When the party takes them down, there are notes indicating someone else was pulling the strings because of reasons.

And if you go this route, listen to your players ideas about what is happening and steal them if they’re better than yours. You end up telling a better story, and they feel good because they figured out the plan.

Quote from Xalthu >>

Caerwyn has some great advice, I’ll just add a little. 

On amnesia, what if one of the PCs dies, or the player moves away and you need a new player or something? How do you add in another character who also has this amnesia? That’s often the Achilles heel for high-concept campaign ideas is what if you need a new character in the mix.

As for making your own campaign, I’d say start small. PCs are in a town, there’s a dungeon over that way and some bandits over that way and the big city is back that way. Sometimes, that can be enough. While an idea of who the BBEG is and what they are doing can help, you can also start with no big ideas, and let things evolve. The PCs go to fight the bandits, one escapes and holds a grudge. Maybe that person becomes a kind of mini-boss opposing them until level 4-5ish. When the party takes them down, there are notes indicating someone else was pulling the strings because of reasons.

And if you go this route, listen to your players ideas about what is happening and steal them if they’re better than yours. You end up telling a better story, and they feel good because they figured out the plan.

 The more experienced I become as a DM the more I realise how vital that last point is. Yes I’ve got good ideas but I’ll never have as many as me and all the players at the table just because there’s more brains involved. Steal ideas from the players if they come up with something interesting and it would logically fit. As Xalthu says the players never even realise if you do it well, instead they think they’ve guessed what you had planned all along and they’ll feel great about how smart they are (and they are smart, just not in the way they think)

And as others have said if it’s a first campaign start small. Even Critical Role started their first campaign in a small village with a small problem. The rest of the world that now fills entire books didn’t exist because it didn’t need to exist until the players went there. Try to draw your world and your story in pencil rather than ink, it’ll constantly change and evolve as the campaign goes on so don’t be too afraid to kill your darlings 

Quote from Caerwyn_Glyndwr >>

The best advice I can give: Do not do this and find a new way to start your campaign.  This kind of start is almost exclusively bad for both players and yourself long term.

Starting with why this is bad for players, a player’s backstory is one of the few places they get to be in the driving seat during an entire campaign.  While the backstory is, of course, subject to DM approval and a dialogue about making it work within the campaign world, it is still a decision players take the initiative on, with the DM being the one responding to the decisions of the players.

Amnesia takes that initiative away from players and puts it back in the DMs hands, with the DM having to either hand wave away some of the amnesia elements to imposing their will upon this element of player agency, creating the very problems that you mention in your post… as well as a general air from the very start of the campaign that you are the kind of DM who will steamroll player agency for the sake of your own narrative.

For your own difficulty, backstories provide the DM a roadmap of “here is what I, as a player, care about. They provide valuable information that you can use throughout the campaign to create tension, make players feel heard, and make players feel they had a hand in creating the world and plot.  A forced amnesia plot sort of overwrites all that - even if they wrote their own backstory and later had the amnesia imposed, they still taints their backstory in a way that can shift their player perspectives and interests.  Moreover, as mentioned above, this creates a negative impression for players of your priorities as a DM, which can make it harder for them to trust you moving forward, and thus make it harder for you to ask them to trust you when the need arises.

The most you should ever do is “you do not know how you go to this specific place” (a pretty standard start) not the kind of “you forgot things important to your character” amnesia you propose here. 

I would also say, stying your entire campaign around going though loss and grief (what I presume you mean by “griefance” based on context) is a very, very, very dangerous thing to do as a DM.  You run the risk of making a campaign that hits far too close to home for your players, many of whom might have strong experiences with grief.  This is the kind of thing where the DM might think they are doing something profound and optimistic, but really could be making a fairly bleak environment that can be insensitive to others’ trauma.  That doesn’t mean that cannot be pulled off - but it needs to be pulled off by a DM who is capable and sensitive of those concerns.  I think you really need to think about that and ask yourself candidly if that is something you think you can handle respectfully. 

This could easily be resolved by simply letting them make their backstory and just coopt details of it.  This easily within the realm of a Modify memory spell.  You have a sister is a real fact.  But your memory is messed with so your actual sister looks different than the person playing your sister.  And if the cultists did their job good, the pretender acts all the ways the player expects that character to be like.   It doesn't undermine the player's choices, but it leverages them to your advantage. 

The real weakness is the inciting incident.   Its way too obvious a tonal shift, unless you're such a good story teller that you can gaslight the players into believing the villagers would be quick to turn on them.   The other common option of sending the party out to help "Stop" something from happening also has a chance of tipping your hand too early, because DMs have a bad habit of insisting a boss fight happen.  Which leaves "loved ones in danger" as one of the few better options, as long as you don't try to imply a time limit.   Time pressure to keep them on track will probably end up derailing things mid-way as the clues start getting dropped.   So you put someone in statis, and thus unhappiness by the group, but not mortal danger.  

For example....  the village "stumbles" onto a temple or something nearby their new township, and one of the PCs "loved ones" gets caught up in the incident.  You fight some monsters to warm things up, and then have someone turned to stone or caught in a magic trap.  Stuck in Statis there are now stakes to free them, but the campaign can run at a comfortable pace.  To really sell it, you can claim the place was built to contain a monster, and have a monster's remains in the room as if an adventuring party already came through a long time ago and slayed it. The reality being that the monster was one of the guardians the cultist dispatched to get to the sealed area, before setting about on this current plan.  If you wanna double dip, you can also take a gamble and have the current party be the one who killed it prior to having their memories altered.  Finding some left behind gear useful to their classes as they worked their way in.  So to free their loved ones, they'll have to recreate a ritual eluded to within the room itself, and have someone of knowledge in the NPCs state that the whole thing was part of some kind of test for some heroes party several years ago. Implying the slain monster was part of that test.  In essence, the trapped NPC is just unfortunate collateral damage of someone else's left over destiny.   

The idea that the left over stuff from some heroes journey poses a hazard to normal folks, like land mines after a long past war, is something I don't see come up very often.  Parties are usually the first to find things.... and prone to leaving a mess in their wake.   So your group being the second party to come through is just unconventional enough that even if the party questions the validity, you can play it straight faced long enough to where them following through is the only way to get to the bottom of it.  And if they get suspicious, but not figured it out completely.... free the trapped NPC first, and make the real ritual a separate epilogue event.  

I'd swap the orientation. Because it's relatively impossible to unknow something, asking player characters to do it is likely to be unsatisfying. NPCs on the other hand, can easily act as odd as you want them to. Have an NPC with a faulty memory, let the PCs interact with them, and then give them the line, "if it could happen to me, it could happen to anyone!" A significant glance at the PCs should be enough to suggest that maybe more is afoot than anyone knows about...

Quote from starlinvf >>

Quote from Caerwyn_Glyndwr >>

 

 

This could easily be resolved by simply letting them make their backstory and just coopt details of it.  This easily within the realm of a Modify memory spell.  You have a sister is a real fact.  But your memory is messed with so your actual sister looks different than the person playing your sister.  And if the cultists did their job good, the pretender acts all the ways the player expects that character to be like.   It doesn't undermine the player's choices, but it leverages them to your advantage. 

For starters, that is not how Modify Memory works - Modify Memory only can modify a memory lasting less than ten minutes which occurred within the past 24 hours. It cannot fundamentally re-write a person’s core memories.  The DM can, of course, make a super modify memory spell go NPCs to use, but that is getting us “outside the realm” of the core spell.

Even beyond not knowing the rules of the spell you lost in your post, I think you fundamentally do not understand the problem I addressed. The reason this steps on player agency is because you are starting the campaign dictating “you already failed some kind of saving throw that causes your own character to have a fundamental part of their identity - their core beliefs about their past to be differently.” This is not a “you can’t remember how you go here” kind of amnesia or a “the last week, which happened after your backstory ended is gone from your memory,” kind of deal.  It is a fundamental shift of an element that falls within one of the areas a player has control over. It also is forced upon the player - at later points in the campaign, something like this can be done if it is telegraphed “the monster you are going up against can rewrite your memory of history” - then it is the players who choose to enter the situation where their backstory memory might be messed with, so they still have agency. 

Finally, what you call “leveraging” the backstory is really more of a it cheap, unearned attempt to pull on their backstory to produce some kind of emotional response from the players.  There is no set up, no building of tension before subjecting a player to such a change - just a DM saying “this happened without any input from you, and because your backstory says you care, you as a player should too.”. That is not a payoff - it is a DM decree of “feel something.”  Things like this tend not to sit well with players, and they take away the ability of the DM to do something similar when there actually might be a real, earned impact.

Ultimately, you are correct - a DM can do this (even if you are incorrect about the method to do so).  However, could does not mean should, and something like this is very likely to create more problems than enjoyment value. 

Honestly OP, this does sound a lot like the new DM problem of "How do i get the players to dance to my tune" and not "How do i give them a challenge they can use as a Dancefloor."
Maybe adjust it a little to keep player agency intact, and don't be too miffed if they work it out and try something different.

Have you considered that maybe it could be not the PCs who have Amnesia or modified memory, but their community?
Cause if you figure out, "Oh gods, someone is mind controlling my loved ones" then you give them a motivation that is theirs, and they likely will figure out "my loved ones are hostages I need to save them."

Their community is convinced they did something. They don't remember doing anything like they are accused of, but they want to keep their loved ones. So maybe they go on these trials. But here is the thing..... Let them figure out problem, then instead of what, the mystery becomes "why?" 
Good way to figure out why is to do the tasks set before them, then let them figure out from the things they are asked to bring back, or things they are asked to do, what the BBEG wants, and in figuring out what they want, they can then start to guess Who. 
"Hey, yeah it might be a good thing for the region if we cleared out beholder cave, but why do they want the central eye so much? Are they trying to nullify some powerful magic?"

 Then let them handle the Who however viciously they want.

Quote from GnollitAll78450 >>

Honestly OP, this does sound a lot like the new DM problem of "How do i get the players to dance to my tune" and not "How do i give them a challenge they can use as a Dancefloor."
Maybe adjust it a little to keep player agency intact, and don't be too miffed if they work it out and try something different.

Have you considered that maybe it could be not the PCs who have Amnesia or modified memory, but their community?
Cause if you figure out, "Oh gods, someone is mind controlling my loved ones" then you give them a motivation that is theirs, and they likely will figure out "my loved ones are hostages I need to save them."

 This is good advice (also love the dancefloor metaphor) about making it a community problem rather than a player one. Get your players to each create a loved one as part of their backstory, a partner, a child, old war buddy, whatever they fancy, and then present those characters as having no memory (or very negative memories) of the players totally at odds with the back story. That's then a problem to solve rather than a situation they have no agency in

I'm going to not so subtly recommend the Crooked Moon adventure. One of the backgrounds and features is an Amnesiac, but all of the so-called fateweaving story threads are built on player backstories and seamlessly integrated into the main plot. Not that you have to do this exactly, but it can gives you a an idea of how this might work. In addition, beside all the super creepy cult stuff and folk lore, there is a hard emotional plot twist not just with the main story, but for each character's arc as well.

Oh my! I didn't expect such an abundance of replies and advices. I could not thank you all enough for your time and knowledge, reading through them all is a fun learning experience! I will surely take each advice into account, thank you again <3

And if you go this route, listen to your players ideas about what is happening and steal them if they’re better than yours. You end up telling a better story, and they feel good because they figured out the plan.

Just to pile on to this point, many of the best reactions I have ever gotten from my players came out of this approach. There is something very satisfying about a hunch being right. Just don't do it every time or they might catch on!