Otto van Dalsen, callsign Rage, was a skilled pilot affiliated with GR Guardian Mercenaries. He was the flight leader of the assassin unit Mimic Squadron, which was comprised of him and his elder sister, Elke.
Despite his aircraft sporting Osean Air Defense Force roundels, he was hostile to and openly engaged Osean fighters. He hides explosive anger and madness behind a cold, calculating persona, and often is forced to keep his impulsive and violent sister in check.
On September 4, 2019, Otto and Elke engaged Strider Squadron, who were escorting an Osean fleet attempting to capture the advanced nuclear submarine, Alicorn. After engaging Trigger, the hitmen retreated from the airspace.
During Operation Domino on September 10, 2019, Mimic Squadron once again attacked Strider Squadron, this time as they prepared to withdraw. Striking Lanza's aircraft with stealth missiles, the siblings engaged the 2 remaining Strider aircraft - Trigger and Count. As the dogfight raged, Clemens contacted the Mimic team on an open channel and ordered them to withdraw. Otto refused, telling Clemens it would be a blow to their reputation. Despite them using stealth missiles and ECM, the siblings were both shot down. In his final moments, Otto cursed the name of Three Strikes, telling the Osean ace he would rather go to hell than eject. Otto's plane then exploded, killing him.
- In Ace Combat X: Skies of Deception, an enemy ace also named "Rage" can be found in the mission The Wasteland. This Ace flies an F-15E Strike Eagle.