How many incidents are there in the Mahabharata, Srimad Vagbat Gita, and Ramayana where riteous people (gods, avatars, or saints) used deception to achieve their purposes?
Can you list those?
Krishna told that Arjuna that Bhima should fight unfairly. He told Arjuna that even the gods have resorted to deception in fighting against the Asuras:
If he were to fight fairly, Bhimasena will never succeed in winning the victory. If, however, he fights unfairly he will be surely able to slay Duryodhana. The Asuras were vanquished by the gods with the aid of deception. We have heard this. Virochana was vanquished by Shakra with the aid of deception. The slayer of Vala deprived Vritra of his energy by an act of deception. Therefore, let Bhimasena put forth his prowess, aided by deception! At the time of the gambling, O Dhananjaya, Bhima vowed to break the thighs of Suyodhana with his mace in battle. Let this crusher of foes, therefore, accomplish that vow of his.
In the battlefield, Drona wanted to know whether his son was alive or not.
Drona became exceedingly cheerless in battle. Burning with grief and exceedingly afflicted, he enquired of Kunti's son Yudhishthira as to whether his son (Aswatthaman) had been slain or not. Drona firmly believed that Yudhishthira would never speak an untruth even for the sake of the sovereignty of the three worlds. For this reason, that bull among Brahmanas asked Yudhishthira and not any body else. He had hoped for truth from Yudhishthira from the latter's infancy.
Yudhishthira's answer.
Fearing to utter an untruth, but earnestly desirous of victory, Yudhishthira distinctly said that Aswatthaman was dead, adding indistinctly the world elephant (after the name), Before this, Yudhishthira's car had stayed at a height of four fingers' breadth from the surface of the earth; after, however, he had said that untruth, his (vehicle and) animals touched the earth.
36 years after the war when Pandavas retired, only Yudhisthira made it to heaven. Yudhishthira was taken to hell when he wanted to see his brothers. Indra told Yudhishthira that he deceived him into seeing hell because he deceived Drona in the matter of his son.
Thou shouldst not yield to wrath. Listen to these words of mine. Hell, O son, should without doubt be beheld by every king. Of both good and bad there is abundance, O chief of men. He who enjoys first the fruits of his good acts must afterwards endure Hell. He, on the other hand, who first endures Hell, must afterwards enjoy Heaven. He whose sinful acts are many enjoys Heaven first. It is for this, O king, that desirous of doing thee good, I caused thee to be sent for having a view of Hell. Thou hadst, by a pretence, deceived Drona in the matter of his son. Thou hast, in consequence thereof, been shown Hell by an act of deception. After the manner of thyself, Bhima and Arjuna, and Draupadi, have all been shown the place of sinners by an act of deception.
According to later tradition, such as Puranas,10 the Maruts were born from the broken womb of the goddess Diti, after Indra hurled a thunderbolt at her to prevent her from giving birth to too powerful a son. The goddess had intended to remain pregnant for a century before giving birth to a son who would threaten Indra.