The Battle of Thunderhead Mountain was a major battle during the War of Sea and Sky between the invading Engelic forces and the Gundarian armies. It was fought by the Gundarian capital of Thunderhead. It ended in a victory for the Engelic army, the later destruction of Thunderhead, and the surrender of Gundar.
After previous defeats, the Gundarian army of 8,000 were retreating back to the stronghold of Thunderhead. At Thunderhead, the garrison numbered 6,000 troops. The main Gundarian force was being harassed by outrider knight and it was feared they would not return without another engagement. Therefore, the last Storm King took his garrison and marched to meet the main force, leaving 300 soldiers behind. Though his storm dragon was large, it wasn't fully grown.
The Engelic force was split into 2 armies. To the south was a force of 6,500 men. It consisted of 850 griffon riders and the rest cavalry. The other army was the main force and held 37,000 men. Of these, 10,000 were trained in archery, around 600 griffon riders, and the rest infantry. The main force had given chase to the Gundarians after their battle. They were to be joined by the southern army which held half of the remaining griffon riders in the north. Due to excellent scouting, the southern army stayed unknown to the Gundarians.
The two Gundarian armies had met in two days from Thunderhead. The king build his camp on a rocky ridge that over looked a field to the edge of a forest. The Engels had set up their camp in the forest to hide themselves from the Gundarians. Overnight, the Gundarians worked hard to build defenses. They collected stones, dug a ditch in the field to stop cavalry charges, and fortified the top of the ridge. During the night, the Storm King led 300 Gundarians to search for and harass the Engels' camp. They were met with heavy fire. They Storm King ended up burning part of the forest with his dragon's lightning breath.
They Gundarians were ready for battle in the morning, excepting the Engels to attack. The Engels waited
The battle saw over 14,000 Gundarians dead including over 190 drake riders falling, the stronghold of Thudnerhead in ruin, and the house of (name) extinct. The Engels had heavy losses on their side with over 11,000 men dead including around 70 griffon riders. The Engels, not wishing to siege the other mountain strongholds or more their southern armies north, decided to enter peace talks with Gundar. After the battle, the cadet branch of the storm kings were sent warnings of complete destruction unless they enter peace talks. Dishearten at the destruction of their capital and a third of their army, the cadet branch would surrender to the Engels and joining their war against the Horans, the Gundarians ally.