//------------------------------//
// Silver 
// Story: Book 1 - The Behemoth came to Canterlot 
// by Equimorto 
//------------------------------//

Twilight turned along with Rainbow Dash, and saw the thing being carried out of the portal. She'd never seen it before, but it wasn't hard to figure out what it might be. Largely black and made of crystal and metal, a central structure longer than several ponies lined together made up of four long crystals held together by circular metal bands at even intervals. One end was free, open, the other attached to a square wheeled piece with a large black sphere at its centre, at least a couple metres in diameter. An arrangement of rune-engraved metal parts connected the two and seemed to allow the long section, evidently the barrel, to position itself at different angles relatively to the sphere, defying gravity as it pointed to the sky. On the other side of the square portion were a set of crystal spikes that evidently served as a control panel.
The duo dodged the bulk of a series of other spells fired at them from different groups around town, while their shield absorbed those they didn't manage to avoid, and all the while they kept their attention on the weapon. So when it turned its barrel to aim at them, as a unicorn behind it activated the crystals with his magic, they didn't have too much of a hard time moving out of the way. They soon realised they'd have to do more than merely dodge the blast though.
First, the sphere crackled with energy, violet bolts swirling and violently moving from its core to its edges. Then the energy found a release as the barrel slid back, the pointed crystal bars touched the surface of the sphere, and sparks went off as all the magic building up inside it began to pour out through them. It bounced between the edges of the path it was constricted into, growing faster and fiercer with each impact, and less than a second after the barrel had moved it was released from the cannon's mouth. A stream of flaming purple energy like a geyser shot towards the sky. It missed the two ponies and their shield, which it was wide enough to envelope whole, but it did not cease.
Twilight and Rainbow realised, as the weapon slowly began to turn, that its attack was not a single blast but a continuous stream. At first it seemed to be following their movements, albeit extremely sluggishly, but they saw quickly where it was truly heading. Lower, and towards the centre of town. Evidently the soldiers had needed to first fire it towards the sky, lest they blow up their own surroundings, but with the way they were pulling the cannon and angling its mouth it was clear where they planned to aim it towards. And if it kept firing at that rate, it would raze to the ground entire sections of the city.
Neither Twilight nor Rainbow needed to say anything, both understanding the gravity of the situation. While still flying around to dodge a myriad of attacks, Twilight fired towards the weapon. Not to stun as she'd been doing for the length of the battle, but to destroy. But her spell reflected off of the shield put up by the soldiers, vaporising a building's corner instead before dissipating towards the sky. Twilight swallowed. "I think I have a plan."