Molten Sulfur Blog

The Battle of Alesia (52 B.C.) was a pivotal moment in Roman and French history. But the ruins of that battle set the stage for an amazing fantasy adventure! The physical remains of the Roman siegeworks present a wonderful obstacle and puzzle, and the history of what happened there sets up some excellent roleplay and plot twists. Let’s look at the battle, how to fictionalize it for your campaign setting, and sketch out an adventure!

In real life, the Battle of Alesia was the climactic final confrontation between the invading Romans, commanded by Julius Caesar, and the defending Gauls, commanded by the Gallic nobleman Vercingetorix. Until very recently before Alesia, Vercingetorix had the upper hand and was forcing Caesar out of Gaul (modern-day France). But a cavalry engagement that the Gauls clearly should have won instead went to Caesar, much to the surprise of both sides. 

Vercingetorix made a strategic withdrawal to the walled Gallic town of Alesia and sent for reinforcements. Caesar built a second wall around Alesia (a circumvallation to keep the Gauls inside), and a third wall behind his forces (a contravallation to protect his rear from Vercingetorix’s expected reinforcements). When the Gallic relief army arrived, both it and the Gallic army in Alesia attacked their respective Roman walls. Tens of thousands of Gauls and Romans died. Caesar narrowly won the day, the mauled Gallic reinforcements fled, and Vercingetorix had no choice but to surrender. Most of the surviving Gauls were enslaved, tens of thousands in all. There were later Gallic rebellions, but nothing that threatened Roman rule like Vercingetorix did. Gallic independence died at Alesia.

For the remainder of this piece, I’m going to keep using the real names (Romans, Gauls, Alesia, etc.) because it’s easy. But this setup should be really easy to fictionalize for the setting of your campaign! Set your version of the Alesia battlefield anywhere there’s been a successful invasion in the past 300 years. Assign the role of the Romans to the invaders, the role of Gauls to the defeated defenders, and make everything else play out pretty much the same way it happened in real life. 

A fictionalized version of the ruins of Alesia and its surrounding battlefield are a great place for a necromancer to set up his lair. It’s remote, no one lives there anymore, it’s full of skeletons to reanimate, and it’s protected by the remains of the Roman siegeworks! PCs could be attracted by the necromancer’s considerable loot, rumors of a treasure overlooked by the Romans and buried under Vercingetorix’s command post, or by the need to rid the countryside of all these undead!

To reach the ruined town of Alesia, the party must first penetrate the remains of the Roman siegeworks, starting with the contravallation (the outward-facing wall). Caesar protected his walls with layers of trenches and traps. The outermost trench is twenty feet wide, nine feet deep, and has vertical walls. The bottom of the trench is a layer of brittle bones, rusted armor, and pitted weapons. It’s a simple Athletics check for the PCs to clamber down into the trench and climb back out. If anyone fails, they fall, land in the rusty detritus, and take a small amount of damage. More importantly, they create a racket. The necromancer’s skeletons inside the Roman siegeworks hear it and will be on the alert. Clever PCs may realize the Gallic relief army had to fill in the trench in places to reach the Roman lines. Fifteen minute’s walk along the (very long) trench finds such a place, and the party can cross without incident.

There are several further layers of defenses. First come the ‘spurs’: pegs with iron hooks. Originally, they were buried. When a Gaul stepped on them, his foot would sink through the loose earth. In pulling out, he would catch his foot on the hook and be very painfully stuck in place. In the years since, the earth has compacted and eroded, and the pegs and rusted hooks now just lie scattered on the field. They should serve as a warning of worse traps to come.

Next are the ‘lilies’ (the Romans had a peculiar sense of humor). These are pits lined with upward-pointing spikes. Each spike is a sharpened log as thick as your thigh. The spikes have mostly rotted away now, but the discarded, rusting weapons lying inside the lilies are just as dangerous. Each pit was originally covered with twigs and brush to hide it. Live bushes have since replaced the artificial cover. Call for Awareness checks. Low rolls are enough to spot that you’re entering a trapped area. High rolls are required to make it through unharmed.

Then come a few defenses that no longer pose an obstacle. The ‘grave markers’ are five-foot-deep trenches lined with sharpened stakes. The stakes are rotted away and the trenches mostly filled in by time. The same is true of two fifteen-foot-wide trenches, one of which was originally filled with water.

The final obstacle is the wall itself: an earthwork, topped with a wooden palisade, twelve feet high in total. The palisade had wooden parapets and battlements so men could fire down from atop it, and towers every eighty feet. Now, the palisade and towers are mostly tumbledown. But there’s plenty enough dangerous detritus to warrant a final Athletics check, especially considering the ‘elks’: horizontal beams reaching out from the wall and studded with long spikes.

The damage taken from failed checks should be higher on the lilies and elks than on the first trench. These booby traps were, after all, intentional. As before, there are places where the narrow trenches were filled in, the spikes cleared, and the palisades torn down by attacking Gauls. Any ‘cleared’ section of one layer has a 50/50 chance of leading to a cleared section of the next layer. If it doesn’t, it means the Gauls were driven back in this spot by Roman javelins, slingstones, and ballistae before the attackers could fill in or tear down the next line of defenses. The Gauls only reached the walls in a few places, but the whole Gallic advance then flowed through these breaches.

Once the PCs get through the contravallation, they enter the Roman camp set up in the space between the walls. Little is left here. Unless enough time has passed for canvas to have rotted away, there are still the remains of tents, each large enough for several soldiers. Many tents are obviously missing. The Roman survivors of Alesia packed out their own tents; those left behind belonged to the slain.

The skeletal dead of both sides, Romans and Gauls alike, now wander the camp under the thrall of the necromancer. (He doesn’t send his thick-headed minions beyond the walls where they could be torn apart by Roman booby traps.) The undead soldiers are dressed in the armor of their people, now pitted with age, and clutch the weapons they favored in life. Romans carry shortswords, javelins, and slings. Gauls carry spears and longswords. If you’re feeling cruel, some Roman skeletons may still remember how to use the catapults in the camp and the ballistae on the towers. Some Gallic warriors may ride chariots pulled by skeletal horses.

(In real life, the Romans of this era cremated their dead. In a fantasy setting, it’s more fun to have representatives of both armies present in the necromancer’s horde.)

If your players are smart, they’ll treat this as a stealth encounter. Tens of thousands died at Alesia. It’s a rare party that can take on two undead armies at once! Fortunately, it’s a big battlefield, and the dead are spread out. If things turn violent, the party can hopefully deal with the nearby skeletons and push forwards (or retreat) before reinforcements arrive.

Ask the two PCs with the best and worst stealth stats what their modifiers are. Roll both in secret. If the un-sneaky one rolled badly, tell the player of the sneaky PC that her clumsy colleague is making noise, so you’ve applied a small penalty to her roll. Don’t forget to factor in any penalties from noise made while crossing the trenches and scaling the palisade. If the total roll for the sneaky PC is high enough to plausibly make it through the camp without detection, announce to the group that, by following the sneaky PC, they are able to sneak past the skeletons and through the Roman camp. Do not tell them what the total roll was.

If they want, however, the PCs can take a risk and poke around in the Roman camp to see if they find anything of interest. Doing so applies a penalty to the earlier stealth roll (the one for the sneaky PC), which may lower the result enough that it becomes a failing roll and they get caught. Do they want to take the risk?

– For a small penalty, the party smells the skeletons. They smell of spring flowers and mistletoe, hinting at the druidic origins of these undead.

– For an additional penalty, the party sees a skeleton wander off into the space between the inner wall and the town. It is torn apart with obvious cruelty by a band of spectral women and children.

– For another penalty, the party finds a buried cache of gold Roman coins left behind by a merchant who died as collateral damage before he could buy any of the surrendered losers as slaves. Also inside the cache is a note detailing the going prices of Gallic slaves in various markets.

Leaving the Roman camp, the PCs can pass through a breach in the circumvallation (the inner wall facing Alesia). This wall is protected with identical trenches and traps to the contravallation, but where there is a breach in the wall, there is a clear path through all the defenses. If the players hadn’t figured out the trick to getting through the traps, this shows them the answer they missed.

Empty fields lie between the Roman circumvallation and the walls of Alesia. This land saw the worst atrocity of the entire siege. The Gallic army in Alesia feared the city would run out of food before the relief army arrived. So as not to weaken the army, the Gallic forces ordered all civilians out of the city. These were women, children, and men too old or too infirm to fight. Caesar refused to let the townsfolk through his lines. He was trying to starve out Vercingetorix before the relief army arrived, and he wouldn’t rid the Gallic leader of so many hungry mouths. But the Gauls refused to let the civilians – their own people! – back into the city. So on the barren fields around their city, the people of Alesia suffered, starved, and died.

In a fantasy world, you’d better believe these people stuck around as angry ghosts. These spirits are intelligent and out for revenge. They have no quarrel with the PCs, only with the men who threw them out and the men who wouldn’t let them pass through. They want to possess the necromancer so they can force him to make his skeletons torture each other. Sure, the skeletons are just the husks of the soldiers who wronged them. But the ghosts of Alesia will still wreak whatever vengeance they can.

These ghosts will want to talk to the party. If the PCs agree to bring the necromancer to the ghosts alive, they’ll show the party a secret tunnel into Alesia, letting them bypass the city wall and the roaming undead inside. They would do it themselves, but the necromancer has ensorcelled the walls of his laboratory (which once was Vercingetorix’s command post) so undead can’t enter it. This protects him from the ghosts, but it also means he can’t summon his creations to help him if he gets into a fight with the PCs.

Alesia sits on a high hill. Its gates hang open. Within, the city is a burned, gutted ruin patrolled by the horrifying products of the necromancer’s experiments. I suggest flameskulls, shadows, and skeletal versions of monsters that died on the battlefield. You could run this as another stealth encounter with temptations to dally (wealth missed by the soldiers, monstrous undead revealing their weaknesses, and the opportunity to observe the necromancer from afar). But ultimately the point is to reach the only building in town that’s intact – though the inconsistent patterns of burn marks and types of stone show it was rebuilt out of rubble once the Romans left. This was once Vercingetorix’s command post. Now it’s the necromancer’s laboratory.

When the PCs encounter the necromancer, it’s important he be willing to talk. (“Wait! I know this looks bad, but let’s talk about this!”) This is potentially a very combat-heavy adventure, which makes it all the more important that it be possible to complete it without any violence at all. Maybe the necromancer can bring the PCs around to his side. Maybe they can bring him around to theirs. Hopefully the PCs will let him tell his story and explain why he’s taken over this site.

While you could make the necromancer some nameless bad guy, I’d reveal to your players that he was actually a historical figure from the war. In real life, a Gallic druid named Diviciacus was an ally of Caesar’s. He even visited Rome! In your campaign, an NPC based on Diviciacus might regret his part in his people’s subjugation. Gaul lost its freedom, perhaps a million Gauls were killed over eight years, a million more were enslaved, and Diviciacus lost his own brother – executed for resisting Roman occupation. One could see him wanting to atone for his actions.

Even though necromancy is traditionally beyond druids, Diviciacus has learned how to extend his own life and raise the dead of Alesia. He believes he’s close to figuring out a magic that will drive the Romans from Gaul forever! He is wrong and deluded. His gods have turned their backs on him for desecrating the dead Gallic heroes of Alesia. Play him as a tragic, misguided figure.

If the PCs want to fight Diviciacus, they’ll find he can still throw down! As his necromancy attests, he’s a mean spell-slinger. He can also change shape into a huge bear, albeit once that’s clearly diseased. If you want to make things tough, he may summon roots to tear down the walls of the laboratory. Since the walls are ensorcelled to keep undead from entering (to protect against the angry ghosts outside the city), tearing them down lets his creations in the ruined city come inside and help their master. (Plus, the falling stones might hurt the PCs.)

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Source: The Landmark Julius Caesar, a collection of works written by Caesar and his contemporaries, edited by Kurt A. Raaflaub and Robert B. Strassler (2019)