Does anyone have any experience running a game like this? The players are the last straggling remnants of a once-thriving undead nation (where the living and the dead were given equal rights, but the undead were primarily in charge) which was annihilated in a Hiroshima-esque atrocity by a legion of overzealous crusaders of a militant sun deity.
They're going to be a mix of undead types (we have a Knight of the Sepulcher, a cannibalistic Childlike Halfling with Tomb-Tainted-Soul, and a Penanggalen White-Haired Witch so far), and will be going Mythic at some point to take on the similarly Mythic challenges of the sun deity's empowered worshipers.
Alignments are more towards the evil end of the spectrum, and while they're short on morals, they're out on a crusade of their own - to rid the world of the sun god who has done so much harm in the name of "Law" and "Good." (They're absolutely right too - this deity is the primary antagonist of the entire campaign world, even for my other campaigns where the players are also good-aligned.)
I want to give them an open-world environment to explore and direct the action on their own initiative - we've discussed not having a pre-scheduled "adventure path" like our recent games, and I'm trying to figure out the best ways to build such a game. Obviously it's not possible to just stat out an entire world, but I want to be at least somewhat prepared no matter what direction the players take their story.
Any advice from GMs who've run similar types of campaigns?
Uh..... well, that's definitely a spin on the usual tropes. Wall of text incoming!
I implemented something similar in my homebrew world, but played it a bit more straight. I'll give you an run-down of the history first, then explain how it may help yours:
One nation (known as "Raiosar") is basically the Lawful Good Sun God Theocratic nation. Every few centuries, they host a "Grand Crusade" against one 'evil' type of creature. The most recent one (a few centuries prior to the most recent campaign, they are gearing up for another in the current timeline of the game) was against "Spawning Undead", specifically Vampires.
Thanks to a custom Divination ("Find the False Father") spell passed down to high level Clerics from Raios (the LG Sun God), they could determine the name and location of the creator Undead by casting it on the corpse of one of the spawn. So... on their Crusade, you had the low-end NPC's and soldiers fighting the armies of nations that had such creatures as they found them and called in higher level 'Hero help' to deal with the Vampires. And then they'd bring the body back to the lead Clerics, who would cast FFF, then depending on the relatively strength of the target, deploy a Hero hit squad.
At that point, it was basically "Scry and Die" with escalating levels of Heroes to kill the more powerful Vampires, finally reaching the Vampire Lords and wiping them out with the top-tier Heroes.
That's what the Heroes saw, anyway. To the poor 'normal people', it seemed as if this LG Sun-worshipping society was filled with self-righteous a-holes who go and start murdering their way through other nations for fun. Once the Raiosaran high command had established all the V-Lords were dead, they called an organized retreat, so their enemies didn't know quite why they pulled out in the middle of a war they seemed to be winning.
Didn't help that they're only 1 of 2 nations that have Firearms, either. They have specific holy hunters who make sure that that secret stays safe, and the only reason the other nation knows is because they are on the other side of the planet and are FAR more advanced.
As far as the players know start out, Raiosar is a war-happy nation which every so often likes to sweep through the world, burning and shooting their way across continents before stopping and going peacefully back to their borders after having wrecked everything. As they level and realize that the point of view of Heroes is a bit more detailed than that of ordinary people, they start to uncover the reasons for these things. Some come to sympathize over time. Of course, some of them are still QUITE angry at this, whether because they are pro-Vampire, or because they find the slaughter of innocents too high of a price to pay. The self-righteous attitude of the Raisaran Heroes certainly doesn't help.
About the only advice you can get that'll be helpful is to plan out the basic 'why' and 'how' things got to where they are, such that there are multiple 'layers' for the players to discover.... similar to my long bit of exposition, above. This will serve to either cause some players to change their minds as they find out more, while others will perhaps be even more focused on ending their sworn enemies when they discover their motivations. It's generally a good idea to stir the Good and Evil pot together such that there are multiple reasons various things are done, and nothing is completely black and white about it. It also adds some fun roleplay when the party starts arguing over whether to oppose or support them.
The other main issue is that you seem to have a 'main plot/goal' of destroying the Sun God. For me that's not a problem simply because that's not the focus of my campaign (there isn't just one), and they can leave the entire nation alone and eventually see the side effects (the next Grand Crusade). But in your case there has to be a way for the players to accomplish the goal of the campaign. You want them to have a sandbox-like setting with endless choices, but in such a scenario they might not know what to do at all simply because there are endless choices.
If they are inventive, they may come up with all sorts of plans. If they are not, they won't, and there won't be much to the main plot since it won't happen unless you squeeze them onto it--but that's the Adventure Path effect you are trying to avoid. And if there's only ONE inventive player, they may come up with ideas that the rest of the party will either follow happily (good for you), or follow grumpily if they feel like that one guy is forcibly pulling everyone along (bad for you).
So... you either hope you get lucky with a bunch of creative players, or you hope you get lucky AND you implement a backup plan. You COULD have some high level NPC with a plan serve as an advisor and quest giver, but if you keep him/her/it alive too long then the party is being led around (like by the creative guy, above). The best option is to have him assist the players early on, and when it seems they are becoming a bit too dependent--have him get offed somehow. Obviously, I have one of these myself in my campaign, but I think I've written enough on the subject for now, lol.
Hope that helps, sorry for the long read.
Great stuff! I like your setting, very interesting.
Hmm. Thinking on it, "gain more mythic power" is probably high on the players' (and characters') priorities, so I bet that dangling a source of mythic power in front of them could entice them down a particular path if it becomes necessary to the story.
Acquiring weaponry or allies capable of assisting with this Sun God would also probably fit well with their motivations.
I'm sure they wouldn't be upset if I had a rough plotline sketched out, but still give them the opportunity to branch out and go "off-script" when they feel like it. We've just been used to more "well, the adventure is this way... hopefully you want to go this way..." style of campaign, where it's pretty clear that there's a "next plot point" that's supposed to happen.