I recently started a new campaign and am coming up with a big bad. I’m making him a Young Red / Blue Dragon hybrid with two heads, called the “Lord of Glass” because when he combines his breath weapons, he can trap his enemies in glass (in my world, blue dragons breath sand rather than lighting). The main idea of the campaign is that the players are working for an adventurers guild, doing various quests while getting hints to the plans and location of the lord of glass. The lord of glass is the leader of a rival adventurers guild comprised of his minions. I’m thinking goblinoids for the minions, but might change them to be more unique. Any advice on how to forshadow him? Maybe the PCs run into his minions who are tasked with the same quest they are?
A small note I’d make is to maybe be wary of the support you get when asking for help in creating your own storylines. People have a tendency to take the ideas you have and turn them into something they’d create of their own design, without real consideration for how it’s your campaign. George RR Martin, Patrick Rothfuss, freaking J.R.R. Tolkien: if any of them came in here anonymously for advice, they’d see other people try and take over the game and not for the better. Honestly, when it comes to creative inspiration you are probably going to do better reading books, watching movies and playing video games. Creative storyline advice in the forums can very often water down your confidence in your own creations with people playing the part of an over the shoulder DM and critic.
TL;DR - Don’t let others wreck your confidence in your own creation.
On to my own thoughts: I feel I really need more on the background, motivations, and general wants of the Lord of Glass before I can comment to much on foreshadowing. Like, what’s his end game. Do you have a mental picture of what he’d be doing that inspires your PCs to care about his plans? Is this more of a subtle villain, with long range goals and sprawling plans, or is he a brute that conquers towns one by one? When I think Dragon I generally think large cavern like dungeons and massive treasure hoards. Is that what this Dragon is about?
Without getting into story hints, here's a few questions to ask yourself in the hopes that answering them will bring you closer to creating a character. Fundamentally at the moment you've got a cool mechanic, not a cool character. So, developing the character that matches this mechanic will help strengthen the enemy.
What is this person's ambition? (What do they want to achieve?)
Not everyone has an ambition but if it's of world changing importance to take out an enemy, this is pretty important. Do they want to bring back a lost love? The enemy might then be raising hoardes of undead in their quest to bring back their dead lover. All other life becomes unimportant in this goal. So, experimentation on others first would raise a mass of enemies that your players are going to fight through. I don't suggest this for your character but rather to illustrate process. Ambition informs the methods by which the character does something and perhaps even why they need to be stopped.
Why is this person evil?
So far what you have isn't an 'evil' person. Head of a rival adventurer's guild doesn't make them big, bad, or evil. What it makes them is an antagonist. And this is fine if what you're shooting for is a rival like Gary in Pokemon. They aren't evil, just different. Now, if they lie, steal, cheat, maim, and kill in order to make their adventurer's guild seem 'better', then you have an evil leader.
As a sub-question to this: is it important that they are evil? Are you happy with an antagonist rather than a bad guy?
What background has this person got?
Much like your player characters, understanding the background of the character is quite important. If they come from money, well maybe they've bought the fame instead of building a 'real' adventurer's guild. If they built it from the ground up because they were a street urchin, perhaps the more murky methods are a result of having learnt to do whatever they needed to do to stay alive? Did they at some point encounter a magic item that corrupted them?
Does this person consider the adventuring party a threat/rival?
A level one player character is going to be beneath the notice of an evil Lich it's fair to say. They are inconsequential. A rival adventurer's guild is slightly different. If your PC guild has less money, well then creating a rival attitude is pretty simple.
The core reason I suggest you ask yourself these questions is that they will also help with the foreshadowing. We can look at popular fiction for examples here. If your bad guy is just evil, then you're writing a childrens book (or modern TV/Film). The Lord of the Rings is a perfect example of this. Sauron is evil. There's no character there, he is just evil. The villain is a poorly fleshed out enemy that just needs to be defeated. And in fairness, given that Tolkien was writing for children, not necessarily adults this is entirely reasonable. Because the bad guy is just plain evil, foreshadowing isn't necessary. It's very plainly stated - evil guy will enslave the world and bring darkness and suffering. It's not clever to try and hide evil, nor is it good writing. It's just plain infantile.
If you want foreshadowing, I suggest reading 'An Inspector Calls'. It's a play that is a masterclass in foreshadowing, but like most adult writing that utilises good quality examples of foreshadowing there is no real 'evil'. It's more the nuanced things that people do which are evil acts. A real evil person doesn't start off as evil, they start off like the rest of us and become evil. The old saying applies really well here 'honest faces usually come attached to liars'. Gerald in Inspector Calls isn't evil for ending a relationship...however that relationship contributes to someone killing themselves. In that story greed and selfishness are the evil, not the individuals.
With that said then and to return to your Lord of Glass, it depends on how evil you want your Big Bad Evil Guy to be. It's worth looking at the currently accepted origin of the term 'Big Bad' in Buffy the Vampire Slayer. As that series progressed, it developed from tales of big scary vampires who were just childish imitations of evil, onwards to the more 'grown up' views of evil: the politician who wanted power; the powerful unempathetic person who wanted to chase their ambition (Glory); earning a living and life itself. Understanding how foreshadowing is used in the Buffy and Angel TV shows are about the best forms of foreshadowing that exist out there in filmed media.
I don't know if you want a big bad, or you want an antagonist from your description. Hopefully, I've laid seeds here that help you to determine that. You don't need to foreshadow someone who is just plain evil with no nuance or depth.
Speaking then to making your Lord of Glass and their minions an antagonist, that's where you can have real fun with the party. If there are three quests on a quest board, maybe by the time the party have completed just the one, the other two have been taken care of by the minions of the antagonist. Off hand comments made by the equivelent of the quest giver could be something like 'oh all the other quests have been taken care of for now'. Or maybe your party 'don't look like the usual sort to be completing quests'. Small digs and chips at the reputation of the party can help with this. Your Party go to find out more information about the quest and the quest giver looks them up and down, 'no, in fact I'll wait for some real adventurers'. Maybe the rival guild have been spreading lies about your party's guild?
Likewise, the party could be at a pub and hear a group laughing at a joke where their guild are the punchline. 'What's more ineffective than the town chamberlian? The PC Guild!'
Of course, you can weave these two threads together. Perhaps the antagonist is actually evil, perhaps they do always kill off threats by imprisoning said threats in glass...however ask yourself one final question: would a murderer of that type really get people accepting their help? There's a reason why mass murderers tend to have news reel of people close to them saying 'oh he was such a nice boy', or 'always smiling'. If the BBEG is really so evil could they have hidden their outright acts of evil for so long that people would provide quests to their rival guild?
I recently started a new campaign and am coming up with a big bad. I’m making him a Young Red / Blue Dragon hybrid with two heads, called the “Lord of Glass” because when he combines his breath weapons, he can trap his enemies in glass (in my world, blue dragons breath sand rather than lighting). The main idea of the campaign is that the players are working for an adventurers guild, doing various quests while getting hints to the plans and location of the lord of glass. The lord of glass is the leader of a rival adventurers guild comprised of his minions. I’m thinking goblinoids for the minions, but might change them to be more unique. Any advice on how to forshadow him? Maybe the PCs run into his minions who are tasked with the same quest they are?
A small note I’d make is to maybe be wary of the support you get when asking for help in creating your own storylines. People have a tendency to take the ideas you have and turn them into something they’d create of their own design, without real consideration for how it’s your campaign. George RR Martin, Patrick Rothfuss, freaking J.R.R. Tolkien: if any of them came in here anonymously for advice, they’d see other people try and take over the game and not for the better. Honestly, when it comes to creative inspiration you are probably going to do better reading books, watching movies and playing video games. Creative storyline advice in the forums can very often water down your confidence in your own creations with people playing the part of an over the shoulder DM and critic.
TL;DR - Don’t let others wreck your confidence in your own creation.
On to my own thoughts: I feel I really need more on the background, motivations, and general wants of the Lord of Glass before I can comment to much on foreshadowing. Like, what’s his end game. Do you have a mental picture of what he’d be doing that inspires your PCs to care about his plans? Is this more of a subtle villain, with long range goals and sprawling plans, or is he a brute that conquers towns one by one? When I think Dragon I generally think large cavern like dungeons and massive treasure hoards. Is that what this Dragon is about?
Without getting into story hints, here's a few questions to ask yourself in the hopes that answering them will bring you closer to creating a character. Fundamentally at the moment you've got a cool mechanic, not a cool character. So, developing the character that matches this mechanic will help strengthen the enemy.
The core reason I suggest you ask yourself these questions is that they will also help with the foreshadowing. We can look at popular fiction for examples here. If your bad guy is just evil, then you're writing a childrens book (or modern TV/Film). The Lord of the Rings is a perfect example of this. Sauron is evil. There's no character there, he is just evil. The villain is a poorly fleshed out enemy that just needs to be defeated. And in fairness, given that Tolkien was writing for children, not necessarily adults this is entirely reasonable. Because the bad guy is just plain evil, foreshadowing isn't necessary. It's very plainly stated - evil guy will enslave the world and bring darkness and suffering. It's not clever to try and hide evil, nor is it good writing. It's just plain infantile.
If you want foreshadowing, I suggest reading 'An Inspector Calls'. It's a play that is a masterclass in foreshadowing, but like most adult writing that utilises good quality examples of foreshadowing there is no real 'evil'. It's more the nuanced things that people do which are evil acts. A real evil person doesn't start off as evil, they start off like the rest of us and become evil. The old saying applies really well here 'honest faces usually come attached to liars'. Gerald in Inspector Calls isn't evil for ending a relationship...however that relationship contributes to someone killing themselves. In that story greed and selfishness are the evil, not the individuals.
With that said then and to return to your Lord of Glass, it depends on how evil you want your Big Bad Evil Guy to be. It's worth looking at the currently accepted origin of the term 'Big Bad' in Buffy the Vampire Slayer. As that series progressed, it developed from tales of big scary vampires who were just childish imitations of evil, onwards to the more 'grown up' views of evil: the politician who wanted power; the powerful unempathetic person who wanted to chase their ambition (Glory); earning a living and life itself. Understanding how foreshadowing is used in the Buffy and Angel TV shows are about the best forms of foreshadowing that exist out there in filmed media.
I don't know if you want a big bad, or you want an antagonist from your description. Hopefully, I've laid seeds here that help you to determine that. You don't need to foreshadow someone who is just plain evil with no nuance or depth.
Speaking then to making your Lord of Glass and their minions an antagonist, that's where you can have real fun with the party. If there are three quests on a quest board, maybe by the time the party have completed just the one, the other two have been taken care of by the minions of the antagonist. Off hand comments made by the equivelent of the quest giver could be something like 'oh all the other quests have been taken care of for now'. Or maybe your party 'don't look like the usual sort to be completing quests'. Small digs and chips at the reputation of the party can help with this. Your Party go to find out more information about the quest and the quest giver looks them up and down, 'no, in fact I'll wait for some real adventurers'. Maybe the rival guild have been spreading lies about your party's guild?
Likewise, the party could be at a pub and hear a group laughing at a joke where their guild are the punchline. 'What's more ineffective than the town chamberlian? The PC Guild!'
Of course, you can weave these two threads together. Perhaps the antagonist is actually evil, perhaps they do always kill off threats by imprisoning said threats in glass...however ask yourself one final question: would a murderer of that type really get people accepting their help? There's a reason why mass murderers tend to have news reel of people close to them saying 'oh he was such a nice boy', or 'always smiling'. If the BBEG is really so evil could they have hidden their outright acts of evil for so long that people would provide quests to their rival guild?
DM session planning template - My version of maps for 'Lost Mine of Phandelver' - Send your party to The Circus - Other DM Resources - Maps, Tokens, Quests - 'Better' Player Character Injury Tables?
Actor, Writer, Director & Teacher by day - GM/DM in my off hours.