The Battle of Stonefalls was fought in 2E 572, between an Akaviri army under Ada'Soom Dir-Kamal and a combined Dunmer, Argonian, and Nord army, commanded by Almalexia, Heita-Meen and Jorunn the Skald-King respectively.
After the sacking of Windhelm, Dir-Kamal moved his army south towards Riften. However, he found the city well fortified and defended by a Nord army under Jorunn the Skald-King, along with the spirit of Wulfharth the Ash-King. Dir-Kamal decided to strike east into Morrowind instead, hoping that the hatred between the Nords and Dunmer would prevent Jorunn from pursuing him. This proved a vain hope, as the Nord army did indeed follow.
In the Black Marsh city of Thorn, an Argonian slave named Heita-Meen was shown a vision from the Hist, showing Nords, Dunmer and Argonians fighting side by side against the Akaviri. She slew both the House Dres Councilman and the Argonian Archein centurion in Thorn, and convinced her kinsman to go north with her. She stopped in Stormhold and gathered more Argonians, including a force of Shellbacks.
South of Ebonheart in the Stonefalls region of Morrowind, a Dunmer army commanded by the Tribunal's Almalexia engaged the Akaviri army. Soon after, Jorunn's army arrived from the west and struck the rear of Dir-Kamal's army. The Akaviri force was vast, however, and the fate of the battle hung in the balance.
It was then that Heita-Meen and her Argonians arrived from the south. The Dunmer were terrified at first, thinking that they had come to aid the invaders, but quickly realized their error as the Argonians attacked the Akaviri instead. Surrounded on three sides, Dir-Kamal was forced back towards the sea. There, his entire force was either drowned or slain.
This victory marked the end of another Akaviri invasion, but more importantly, the cooperation of bitter enemies would lead to the formation of the Ebonheart Pact soon after.