Ravana's abduction of Kausalya, Rama's mother
Ravana once approached Brahma, inquiring him as to how his own death would come about. Brahma responded that the son of Kausalya and Dasharatha would be the cause of his death. Enraged, Ravana abducted Kausalya immediately prior to her wedding, and placed her in a box on a deserted island in the middle of the ocean.
The sage Narada described her whereabouts to Dasharatha, who then brought his army to the shore to rescue her. The army began to cross the ocean in boats, approaching the island of Kausalya's captivity. Hearing of Dasharatha's rescue attempt, Ravana sent his "rakshasa" (demon) army. In the ensuing battle, Dasharatha's army was annihilated, but Dasharatha escaped on a wooden plank, floating on the ocean for many days.
Eventually, he landed on the island of Kausalya's captivity and chanced upon the box in which she was enclosed. Narada and other sages quickly arrived and performed a wedding ceremony, after which Dasharatha and Kausalya were enclosed in the box.
Unaware of these events, Ravana went to Brahma and told him that his prediction had been rendered false, as he had killed Dasharatha and was holding Kausalya captive in the box. Knowing that his words must always be true, Brahma had the box brought to his and Ravana's presence and opened. Seeing Dasharatha and Kausalya in the box, Ravana was humiliated and planned to kill them both, but his wife Mandodari persuaded him otherwise. Eventually, Dasharatha and Kausalya went to Ayodhya, where they lived happily. Eventually she gave birth to Rama, and his three brothers.
Ravana’s Abduction of sita
When Hanuman first arrived in Lanka, he searched everywhere for Sita. At one point, he mistook the sleeping Mandodari for Sita. Realizing his mistake, he wondered why she looked like Sita., who was listening to the story from Shiva, asked why there was a similarity in their appearance. Shiva responded that Ravana's mother Kaikasi had once sent Ravana to Shiva to obtain a beautiful Shivalinga for her. Ravana had pleased Shiva and given him two boons, one of which he used to obtain the Atmalinga. With the other, he asked for Parvati as his wife. Shiva gave both to Ravana but told him that if he dropped the Atmalinga, it would remain installed where it fell and would move no further. And so Ravana departed with Parvati and the linga.
Parvati called vishnu for help, and he appeared to Ravana disguised as a Brahmana. The Brahmana told Ravana that he had been misled and that the Parvati, she gave him was really a fake version. The real Parvati, he said, was in the netherworlds hiding from him. Ravana then entrusted the linga to the Brahmana, and set off in search of the ‘real’ Parvati. After Ravana had left, the Brahmana (Vishnu) consecrated the linga and departed. According to the Ananda Ramayana, this is the origin of the linga at Gokarna.
Ravana eventually returned to Gokarna to perform the intense tapas, which later earned him the boons from Brahma that made him invincible to everyone but humans. Thus Vishnu was later able to incarnate as Rama in order to defeat Ravana. But that story doesn't mention in Valmiki Ramayan or other Ramayana except for Ananda Ramayan and many scholars rejected that story.
