Zavala has forbidden Guardians from traveling to the Reef for fear of starting a war with Uldren. So, officially, Ikora can't help you.
But unofficially, Ikora tips you off that Uldren and his Fallen Barons have gathered on a stretch of the Reef known as the Tangled Shore. If you want revenge, there's the place to start.
Take a hint from Ikora and investigate the Tangled Shore in mission "High Plains Blues."