I took my players to the Argonne Forest

You heard me! The group had just finished up their business at a set of standing stones, a local font of magical power. They received ascending from Ulfin, requesting their assistance. He showed up moments later, asking if they'd be willing to directly assist the war effort. A Vanguard force had found themselves surrounded a day prior. It was the perfect opportunity to showcase the power of the runes, and Ulfin needed a group comfortable hitting above their weight class. The group was relatively happy to assist, and I think they were somewhat excited to test their mettle against an organized opponent. And so they went off!

Ulfin used his usual transport via plants to drop the group off at an encampment of soldiers from Garamentes. The Captain fills them in. A few of the advance force moved too far in, and either didn't receive the retreat order or didn't think it was legitimate. Either way, they're surrounded, low on supplies, and soon they'll have more wounded than men in fighting condition. The group's job is straightforward; smash through a bunker too heavily fortified for their regulars to handle. 

The encampment has howitzers, and a few shells remaining. They can't produce any serious bombardment if they spread their shots. With the party striking the most heavily defended choke point, the main force can rain hell on the flanks, allowing their men to penetrate any defensive line. 

One final point; the vanguard only had 1 spellcaster, who was unresponsive after their last sending. 
An unidentified archmage had engaged them. 

The group settled in, and come morning the trench whistles shrill cry sent them off. I laid out the first battle map; I'd taken a great deal from BF1's Argonne Forest map. The players have a few rows of trenches and barbed wire to cross before coming up on a bunker. The only creature immediately visible was an ogre holding a ballista-sized crossbow. The party engaged!

As they moved forward, they encountered a set of Tyrant Regulars, a hobgoblin legion employing weapons like crossbows, rapiers, and whips. They fired from the trenches before going prone. The party took some hits before moving into melee, diving behind cover before finally getting in their faces. Right as they reached the last trench, two sets of creatures emerged. First, two Tyrant Captains came from the bunker, tossing blastcap bombs (combustible, easily grown mushroom with incindiary materials) at the party. Next, an ogre carrying a small fort came from a side path, leading to train tracks (keep that in the back of your mind for now). 

The fort held four goblins of the Powder Horn Legion, all wielding muskets. On arrival, they sent a volley towards the Paladin, Sorcerer, and Artificer, all crouched behind cover. The ogres from that point were quite heavily focused. The party mages took them down as the Cleric and Paladin moved into melee with the Tyrants. The Howdah Ogre fell, along with his cargo, sending the goblins spilling out. They’d by this time finished reloading, and sent another volley towards Alan the Paladin, to little avail.

Once both the goblins and ogres were dispatched (along with a majority of the Tyrants), two of the Tyrants managed to escape. The fled into the bunker, sealing one of the two doors shut. The party attempted (and failed) to bust through, before attempting to enter the other door. It was unlocked, lucky them! It was also trapped. A blastcap bomb detonated in their faces. Inside this front area, they found spare bolts, rations, rain capes, coils of barbed wire, etc.

The party continued through a long hallway, until they came up on beds with plaster dividers between them. I had the party roll perception, and they failed; Tyrants emerged, and began unloading. They started with a volley of crossbow bolts before clustering next to the edges of the hallway, waiting for the party to emerge. The party engaged, quickly recognizing these were stronger than the last. The Sorcerer Sael cast polymorph on Asura the Cleric, turning him into a giant ape. The ape gave full cover to the party (good for them) but also almost entirely blocked movement to the Tyrants (good for me). What ensued was primarily Asura striking the Tyrants as they desperately tried falling back. They put up a decent fight, taking the ape down by about 100 hp, but not enough. Asura burst through the other side of the bunker, the crumpled bodies of Tyrants around him.

At this point, I asked the players to roll a d4. 2 was the result; they heard the whistle of a train. They looked around, prepared themselves with what little they could (the party had at this point expended almost all of their spells), as an armored train rolled through.

Now, siege equipment/armaments takes time to load, aim, and fire. YOu only have all 3 in the same round if multiple people are operating the equipment. The train had 5 armaments of varying size, each manned by one person. Asura (still a giant ape) immediately set to attacking it, wrecking the center gun. After a natural one on an attempt to flip one or two of the rail cars, he draped himself over the train. The guns to either side fired at point blank, leaving him unconscious next to it.

The party engaged, trying to get to Asura before he died. Dr. Silver (the party artificer) opened up a small bunker next to the train, finding…two Tyrant Knights. What followed was a chase around the battlefield as certain party members tried to catch the attention of the Tyrants as the others attacked the train. Asura was up in about two rounds, and cast Spiritual Guardians. There were screams from the 3 cars next to him, which then stopped. Kevin playing his regrettably short-lived sorcerer (spoiler warning) started throwing blastcap bombs at the hatches on the other two cars, which were at that point retreating.

Kevin’s character actually climbed the car and got inside (after successfully blowing off a hatch) and gutted one of the engineers. The cards continued moving back, and after dispatching the Knights, the party gave chase.

At last, the final map was laid out. Simply a brick bridge over a slight depression, tracks leading over it. Kevin’s character had at this point killed the last engineer, and managed to stop the train on the bridge. He’d also accidentally unloaded a shell from the siege howitzer in his car. The rest of the party arrived, sounds of battle on the flanks, and above a hill some hundred yards ahead of them. This was the final stretch; where was the enemy?

A slow clap rings out, seemingly from all around them. Someone starts congratulating them on their progress, but regrets their journey must be cut short. Undead start rising from the ground, and its initiative. It starts out simply; the zombies don’t have a high armor class or to hit chance. Asura pops Channel Divinity, destroying undead in a 30 ft radius. Here, the strange voice’s owner reveals himself. Decked out in black with a white, engraved mask, our friend raises more undead. Morover, he begins casting spells through the undead around him, their bodies twisting and jerking to match his commands. The battle actually doesn’t go too poorly by and large; zombies prove largely incompetent except acting as remote spellcasters, and the archmage doesn’t have a terribly impressive number of hitpoints. Nevertheless, he is whittling down Asura and Alan’s hitpoints. Kevin’s character has, in the meantime, been re-loading and aiming the siege howitzer attached to his car. The archmage’s turn is coming up, but Kevin and 1 other go before him. The archmage here has roughly 25 hp. Alan and Asura are clustered around him.  Kevin’s character fires the siege howitzer. I have him roll an attack. Even if he rolls above AC, it won’t necessarily hit, and almost certainly won’t be a direct hit. He rolls: natural 20.

Kother and the Zombies around him are obliterated. I have Kevin roll 10d10 and double the result, and ask Chris and Dennis to roll dex saves. Chris, playing Alan, succeeds! Dennis, playing Asura, does not. The total result of the damage is 106 or 112, I can’t recall. Alan gets to halve that damage, but Asura will not. Asura is actually killed outright, but Alan intervenes. He uses an ability from his subclass to take the damage on himself, keeping Asura alive but unconscious, and killing Alan outright.

Asura is brought back up with potions, but he has no spells for Revivify. In fact, all he has a first level spell slot; he can’t cast something like Gentle Repose to extend his window on reviving Alan. There’s one way, however. Expending a first level slot,  he casts the Blood Rune, allowing him to cast a second level spell. He casts Gentle Repose, giving him a chance to revive Alan once they rest.

The other party members, in the meantime, have a talk with Kevin’s character.

Kevin’s character is not longer with us.