First Aurelian Crusade
During the First Aurelian Crusade, Ronahn aided Idranel in her assault on Angel Forge on planet Meridian. As the Farseer and her main eldar warhost headed towards the forge, Ronahn remained behind in a guard tower in an attempt to slow the advancing Blood Ravens . Upon meeting them, he vowed to avenge the death of Nemerian, a renowned Exodite Ranger who was killed by the Space Marines previously.
Third Aurelian Crusade
Ronahn reappeared as a former Pathfinder of Ulthwé, having survived the events at Angel Forge but renouncing his ties to the Seer-led Craftworld and now wandering the stars. He remained loyal to his race, assisting them when called upon, and found himself allied with Kayleth.
Later in the Eldar's campaign he revealed that he is the brother to the Farseer Taldeer and had nightmares of his lost sister. He was infuriated when he found out that Azariah Kyras was involved in interrogating and executing his sister. Ronahn was determined to recover his sister's spirit stone, which Kyras kept as a trophy. After defeating Kyras, he retrieved her soulstone and said he would return her to Ulthwé.
Ronahn is skeptical towards the Eldar's reliance on prophecy, and sees their current mission as a waste of effort. Unlike many Eldar, Ronahn actually has shown pragmatism and even realism. His source of cynicism may be because of Taldeer, who preferred to believe in her prophecies instead of taking rational choices like fleeing for her life even when she knew everything was lost.
Along with his cynical nature, Ronahn also poses a sharp wit, going as far in mocking Kayleth for her over-use of direct confrontations rather than using cunning, and mocking Veldoran for his reliance on prophecies. When he was mocked by the Warlock for being experienced at running away, Ronahn slyly pointed out that the only Eldar still alive today were those who ran.