The Gathering Forces

During the night, while the party is getting their rest, several things are happening at the same time. A large army of kobolds, led by several ogres and other villains pours into the valley around the central hill from tunnels and paths all around. Within the tunnels below the fortress, another band of creatures is tentatively making their way out into the dungeons.

Moving forward out of the Underdark on the trail of the grimlocks, a large group of svirfneblin makes their way into the fortress complex. The grimlocks broke through from their own tunnels into the labyrinth dug by the kobolds, rushing forward to attack the players. Now, it turns out they were likely being driven out by the band of svirfneblin. 

The final watch of the party will note the arrival of the crawling horde on the plains below as the sun creeps over the ring of mountains. Shortly thereafter, three svirfneblin will make their way into the party's presence, requesting a meeting. In brief, the entire hillside is surrounded, but you are not alone in your defense. The gnomes have secured the lower entrance, which is also threatened, and have sent runners back to their underground city to send reinforcements.

With the growing light, you note ogres and two large brutes that seem to be made of the mountain itself, earth elementals. The svirfneblin assure you they have xorn coming with the balance of their forces, and that they will arrive soon.

In the full light of day, it becomes apparent that other creatures have been drawn to the valley. In the distance, on the slopes of the icy heights, you notice several yeti, and on another hill a shifting image of large dogs, stealthily taking in the proceedings. A Survival check (DC16) will recognize them as blink dogs.

Through much of the morning, little appears to be happening. Suddenly, the army seems to surge forward as one. They advance on the hill, tightening their pincer grip. Then two groups of 20 kobolds, each led by an ogre, and surrounded by 5 winged kobolds, break away from the others and charge up the mountain toward the ruined buildings of the fortress. One groups is coming directly at the party's location, while the other one is rushing toward a mostly intact building several dozen feet away. The leader of the svirfneblin will send a companion back into the tunnels to call more troops, then head forward with his other companion to meet that attack. Five others will come from the dungeon to follow them forward. 

The kobolds will send another two waves forward after a short rest once the first has been dealt with. If their numbers are greatly reduced, the sally will retreat and regroup. After three attempts, the kobolds will settle in for a long rest to consider their options.

Soon, the big boys will enter the battle, and things will open up on a second front, but that is good for now.