In the Bala Kanda of the Ramayana, Rama is hesistant to kill the Rakshasi (demoness) Thataka because she's a woman, but the sage Vishwamitra tells him that even Indra king of the gods has fought women when they were engaged in evil:
Compassion regarding the elimination of a female is ungermane, oh, best one among men, since a prince has to effectuate it intending the welfare of four categories of society.... To the nominee who bears the burden of kingdom this is the age-old duty, and hence oh, Rama, the legatee of Kakutstha, eliminate this infamy, as goodness is inevident in her, isn't it? Oh, Rama, the protector of people, we have heard that Indra once eliminated Manthara, the daughter of Virochana, when she wished to annihilate earth, haven't we?
Well, "we" may have heard about this, but I haven't! So my question is, what is the story of Manthara daughter of Virochana? For those who don't know, Virochana was a famous demon killed by Indra. He was the son of Prahlada and the father of Mahabali. So that would make Manthara Mahabali's sister.
Unfortunately, the Puranas often focus on male genealogy, so they're not much help here; the Vishnu Purana just says "Prahláda had a son named Virochana; whose son was Bali" and similarly the Srimad Bhagavatam says "Prahlāda had one son, Virocana, whose wife gave birth to Bali Mahārāja." However, later on in the Ramayana there is some indication that Virochana had a daughter; this excerpt from the Uttara Kanda of the Ramayana describes the wife of Ravana's brother Kumbhakarna:
[T]hat master - Lanka's lord - going (back) to the city married his brothers. And Ravana married the grand-daughter of Virochana (on the maternal side) named Vajrajwala to Kumbhakarna.
So assuming Virochana had only one daughter, that would make Manthara Kumbhakarna's mother-in-law!
In any case, what is the story of Manthara's attempt to "destroy Earth", to the point where Indra needed to kill her? By the way, Virochana's daughter Manthara is not to be confused with Virochana's uncle Mandara, whom I discuss in this question. (And she is different from Kaikeyi's evil servant Manthara, although this translator claims that Kaikeyi's servant Manthara was named after Virochana's daughter.)