Outlander

It takes all day for the preparations to be complete. You have not done this spell before and it is not supposed to work on this magnitude, but you work slowly and carefully. As the sun begins to set, you hear the sound of a goblin horde in the distance. You hurry in the gates and reach the top of the wall to confirm your assumptions. Thousands of invaders are marching on the castle, you can see the ivory shine of their teeth in the torchlight. The Horsemaster ordered his troops to begin firing arrows, but only at point more than fifty paces from the wall. At first, the goblins seemed encouraged by this as dozens begin to climb the walls in earnest; passing their companies who fall in the field behind them. But you and the Horsemaster have a plan. as soon as the first goblins reach up over the edge, you whisper the trigger Word.
Immediately, the wall becomes engulfed in a storm of lightning. All of the climbing goblins fell to their death and then your soldiers pressed their advantage. The Falcons manned catapults and rained stone upon the invaders. The bowmen fired relentlessly. Horsemen stormed through the gates behind Merida and chased down the stunned goblins on foot.
"Back you beasts!" you suddenly hear. It sounds like the Horsemaster is battling goblins on the wall. He may need your help, but can you abandon your post this close to victory?