The Tower of Ishal, is a location in Ostagar. Before the Battle of Ostagar, Teyrn Loghain devises a plan to defeat the darkspawn: The Grey Wardens and King Cailan's troops will engage the darkspawn in combat, then someone will light the beacon in the Tower of Ishal, signaling Teyrn Loghain to attack the darkspawn with his men. The Warden is selected for lighting the beacon. However, during the Battle of Ostagar the darkspawn break into the tower through an underground tunnel and slaughter the guards. The task of lighting the beacon apparently will not be so simple after all...
Background
The Tower of Ishal was constructed by the Tevinter Imperium along with the rest of Ostagar during the height of its power. The tower was named after the Archon that ordered its construction as well. After the First Blight the whole of Ostagar, along with the tower, was abandoned and fell into disrepair but the tower still stands strong several hundred years later.