In this chapter of the Vana Parva of the Mahabharata, Yudhishthira is in grief because of the year in hiding the Pandavas are about to start. So the sage Dhaumya cheers him up by reminding him that the gods have gone into hiding for the purpose of defeating their enemies:
O king, thou art learned and capable of bearing privations, art firm in promise, and of subdued sense! Men of such stamp are not overwhelmed by any calamity whatever. Even the high-souled gods themselves have wandered over various places in disguise, for the purpose of overcoming foes. Indra for the purpose of overcoming his foes, dwelt in disguise in the asylum of Giriprastha, in Nishadha and thus attained his end. Before taking his birth in the womb of Aditi, Vishnu for the purpose of destroying the Daityas passed a long time unrecognised, assuming the form of the Haya-griba (Horse-necked). Then how disguising himself in the form of a dwarf, he by his prowess deprived Vali of his kingdom, hath been heard by thee! And thou hast also heard how Hutasana entering into water and remaining in concealment, achieved the purpose of the gods. And O thou versed in duty, thou hast heard how Hari with the view of overcoming his foes, entered into Sakra's thunder-bolt, and lay concealed there. And, O sinless one, thou hast heard of the office the regenerate Rishi Aurva at one time performed for the gods, remaining concealed in his mother's womb. And O child, living in concealment in every part of the earth, Vivaswat, endued with excellent energy, at last entirely burnt up all his foes. And living disguised in the abode of Dasaratha, Vishnu of dreadful deeds slew the Ten-necked one in battle. Thus remaining in disguise in various places, high-souled persons have before this conquered their enemies in battle.
Now most of these stories are recognizable. Hayagriva is the horse-headed form of Vishnu that I discuss here. The "form of a dwarf" is a reference to Vishnu's incarnation Vamana. Agni (Hutasana) entering the water refers to the story described in this chapter of the Vana Parva of the Mahabharata. Vishnu entering Indra's thunderbolt is a reference to the story of Indra killing Vritrasura. Aurva being "concealed in his mother's womb" is a reference to the story of the Vadavagni fire which I discuss here. And Vishnu "being disguised in the abode of Dasaratha" is obviously a reference to Rama.
But my question is, what is the story of Indra dwelling "in disguise in the asylum of Giriprastha, in Nishadha" for the purpose of defeating his enemies?
First of all, is Giriprastha a person or a place? Some books say that the Mahabharata mentions Giriprastha as the capital of the kingdom of Nishada, but they cite this very Vana Parva chapter as their source! So they may just be misinterpreting things.
In any case, in my answers here, here, and here, I discuss how Indra went into disguise to defeat the demons Prahlada, Virochana, and Vyamsa, respectively. But did any of these stories take place in the kingdom of Nishada?