Anti-Wagon Adhesive Lance

Alistair gave the Blackheart a look. "Travers, I haven't seen you at the Association in a while. How have you been?"
Hugo Travers gave Alistair a smile that failed to extend to his eyes. "About as well as someone cooped up in an apartment a season could hold up, I suppose, Alistair." The battlemage cracked his neck. "Apparently the Ground Forces want to keep me in the Capital City, for reasons known only to them, but it's painful that I can't leave my apartment without being recognized."
Well, there was an obvious reason for that. The Blackheart had turned four men into meat after a robbery attempt, and it was breathlessly reported on for nearly three weeks. Alistair nodded. "Well, at least here we're only practicing against a dummy target."
The colonel standing at the Wizard's Association proving grounds turned to them, then gestured to the table. Six adhesive lances were on the table, with two very old power-wagons parked across the grounds, roughly fifty meters away. "Gentlemen wizards. We'll commence the test immediately. I'd like each of you to, using magic, lift, light, and launch three adhesive lances at your corresponding wagons, and launch them as fast as you can. We'll do the direct impact test on the morrow for comparison; today is only a lance test."
Travers stepped forward and gave the colonel a brusque gesture; the man scurried to the side. Without raising a finger, the Blackheart magically lifted one lance, and it caught fire in midair as he concentrated on its tip. He launched - too fast! The lance pushed forward but exploded in midair, spraying heated glue in a spatter over the grounds. 
The Blackheart grimaced and lifted the next lance, igniting it along its length. The next launch was slower, but still as fast as any arrow shot by a hunter; the lance smashed into the side of the wagon tip-first and shattered, spreading glue along the edge. The third lance was right behind it; Travers had managed to lift and ignite his third lance while launching the first. 
Alistair nodded; it was his turn. With a gesture, he focused on one of the lances in front of him, and it slowly began to rise. He concentrated on the local leylines, pulling two into the tip of the lance with his mind's eye, and the lance began to heat, before catching fire. Instinctively, Alistair pulled his hand back, as though readying an actual javelin; the lance launched with his throw. His launch was slower than Travers, and the lance nearly missed; the wizard had to correct the lance mid-throw, but watched with satisfaction as it struck the exposed wheel of the wagon, spreading glue into the axles.
He was about to prepare the second when he heard a clapping. The colonel had stepped back out. "Alright, alright, that's a good enough test." He pointed to the first wagon, which had tipped over as a result of Travers' third lance hit. "No need to spend any more lances, we'll test with pole strikes tomorrow, but adhesive lances are for-sure effective when magically launched. Expect both of your names in the military dispatch journal next week, gentlemen, and thank you again for your support."

Utility

Doctrine calls for anti-wagon lances to be issued to specialized infantry trained to counter wagon attacks. These infantry can either lay in wait alongside a road, waiting for a wagon to pass, or stand in formation and present a target for wagons, jumping aside at the last moment and thrusting their lance at the wagon. Most assault prows are fully armored in the front, presenting a sheer metal surface that is impervious to such glue attacks, but most wagons cannot carry armor of similar quality around the entire vehicle, and especially not the exposed drive wheels. An adhesive lance directly into the drive wheel will break, gumming up the wheel and launching a half-gallon of glue into the gearing driving the axle.
Trials have demonstrated that a trained lancer can successfully disable a wagon on the attack about a third of the time, which has been deemed a high enough success rate to be worth deploying on the field. Lancers themselves, charged with literally running at and striking a fast-moving power-wagon, face a subsequently higher risk of death.

Manufacturing

As major warfare has not broken out in a century, a single manufactory line in the Etoile Capital City manufactures Adhesive Lances, cycling the available supply. While they are conceptually simple, the interior measurements of a lance are a state secret, as the exact thickness needed for the lance to be reasonably strong but consistently shatter on impact was refined over many development iterations.

Social Impact

While lances have been a favored defensive weapon for generations, evoking the ancient infantry spear formations of prehistorical warriors, the rise of Magic has led to a re-evaluation of lance utility, as a wizard could feasibly halt a wagon, or magically fling large objects at it to stop its forward progress. The newness of Magic has subjected all existing combat doctrines to review, and there is a significant chance the adhesive lance could go the way of the medieval lance of old.

Access & Availability

Specialized 'lances' that contain the glue and metal mixture in the shaft were developed, for use by infantry expecting to be attacked by prows. These are military weapons, and readily available to the Etoilean Ground Forces; ownership by private individuals is prohibited due to the risk of these weapons falling into untrustworthy hands.

Complexity

For weapons intended to counter the most technologically advanced weapon on the battlefield, the lance is quite simple. A long, ten foot pole resembling the jousting pikes of old, the shaft of the lance is hollow, prefilled with a glue and nail mixture from the manufactory. When deployed to the battlefield, the lance is wrapped in oily rags; these rags are set alight by the infantryman when wagon attack is imminent. The adhesive lance will shatter on contact, triggering a loaded spring that launches the glue mix directly out of the shaft and onto whatever the lance has struck.

Discovery

While the Principality of Etoile developed Power-Wagons and pioneered their usage in warfare during The War of Unification, it was obvious that conflicts going forward would likely involve powered attack prow cavalry on both sides of a conflict. Prepared defensive fortifications and trenchworks could neuter these wagons on the attack, but those defenses take time to construct; a more immediate solution was needed to allow infantry a fighting chance in an attempt to disable a moving wagon.
A crash research team settled on an ingenious solution - a mixture of heated glue epoxy and regular steel nails, when thrown at a wagon's vulnerable axles, would severely damage the vehicle, covering the control surfaces with glue and gumming up the gearing with nails. While sheer momentum would not result in the power-wagon's immediate stoppage, a successful hit could disable the vehicle's mobility, rendering the cavalrymen riding the prow vulnerable to infantry attack.