The Battle of Sancre Tor took place in 2E 852, and was a battle fought in the Jerall Mountains where General Talos retook the old mountain fortress of Sancre Tor from Nord and Breton forces and gained the service of the Nords in his conquest of Cyrodiil.
General Talos, serving King Cuhelain, prepared to assault the fortress with an army that was tired, cold and ill-equipped to mount an attack on the walls.
Talos left a small force outside the main gates of the fortress, tempting the Nord-Breton forces into a sortie. Meanwhile, the main bulk of his forces approached from the rear, gaining entrance to the fortress through a secret passage in the unscalable rear, revealed by a turncoat. This turncoat is traditionally a Breton sorcerer. The now undermanned fortress was then taken by Talos' forces, who captured the generals within the fortress and compelled the surrender of the Nord-Breton forces engaged in the sortie. The Blades also played a role in Tiber Septim's victory at Sancre Tor, to honor this role, Tiber Septim gave the Armor of Tiber Septim to the Blades.
The Nord captives swore allegiance to Talos after the battle, and played a key role in Tiber's campaigns to unite Cyrodiil. The Breton Battlemage command was summarily executed. Talos recovered the Amulet of Kings from the tomb of Reman III in the catacombs beneath Sancre Tor immediately after the battle. Tiber Septim also received the blessing of Akatosh inside the catacombs.
Some sources claim this attack damaged the fortress so badly it had to be abandoned, while others say that it was abandoned some time after the battle due to its poor strategic value. However, the truth appears to be that the citadel was cursed by the Underking, causing it to be sealed by the Grandmaster of the Blades some decades after the battle.