Confrontation on the Broken Isles

But Illidan's servants had not been successful in destroying the boats. Maiev and the Watchers arrived on the Broken Isles shortly after Illidan, and the two forces battled across the watery terrain. Illidan reached the tomb, and Maiev was quick to follow. With Gul'dan's knowledge, Illidan quickly traversed the Tomb and came to the chamber which contained the Eye of Sargeras. Maiev came upon him as he and Vashj were activating the powerful artifact, and, as vengeance for her imprisoning him for ten thousand years, Illidan used the Eye to bring the Tomb down around her, and then quickly escaped through the underwater passages used by the naga. Though he killed Naisha and all the other Watchers within the Tomb, Maiev escaped with her magical abilities. On the surface, Illidan and Maiev battled for supremacy as the Warden sent out a runner to gather reinforcements from Ashenvale. 
 
Illidan after recieving the Orb of Kil'jaeden.

Malfurion and Tyrande arrived on the Broken Isles with reinforcements as Maiev's base was being overrun. When they struck back, Illidan's forces crumbled, but he and his retainers fled before they were seriously harmed. Tyrande pursued them out of the base, and Illidan ensnared her to protect himself, and then warned her not to interfere. He fled across the sea once again. During this battle, Tyrande finally revealed why she had spurned Illidan: too drunk with his rising magical and political power, he had forgotten his own inner strength. Malfurion, despite his increases in power, held on to that strength within him. Armed with this knowledge, Illidan finally came to grips with his feelings. 

Illidan landed on the shore of Lordaeron, and quickly made his way through the Silverpine Forest to get to Dalaran, where Illidan began to use the Eye of Sargeras to break apart the polar ice cap and destroy Icecrown and the Frozen Throne. But he was interrupted by Maiev and Malfurion, and the spell failed. Malfurion had felt Illidan's spell tearing the land apart and concluded that he was a danger to the world and had to be stopped. Illidan, who was entangled by his brother, called Malfurion a fool as he was destroying the Lich King, their common enemy. Malfurion was furious at him for causing the loss of Tyrande, who had been, according to Maiev, killed. Illidan was heartbroken that the woman he loved was dead, but Prince Kael'thas, the night elves' newest ally, thought that perhaps it was premature to presume her dead. Kael'thas explained that Tyrande had not been "torn apart" by the undead, as Maiev had told Malfurion, but had instead fallen into a river and been swept away by the currents. Malfurion immediately arrested the Warden and promptly went in search of Tyrande. Illidan begged to be allowed to help his brother track down the beloved priestess. Illidan and his personal guard of naga found Tyrande under heavy attack from a massive undead force. 

Illidan and his naga battled their way through the undead until they reached her. Tyrande was taken aback by Illidan's service to her, and when he delivered her safely to Malfurion, she was astonished. Malfurion told Illidan he was free to go on the condition that he never threaten the night elves again. Illidan, wishing for an end to the conflict with his brother, agreed.