A part of me wishes that Dadhichi hadn't been built into such a major prominent role, particularly given that I've not read about him doing so many things. The only thing I know about him is his sacrificing his life so that Indra could make the vajra.
The side story - once when Indra refused the Ashwini twins some knowledge that they wanted to gain, they approached Dadhichi. Dadhichi told them that he had been told that if he revealed that particular information to anybody, his head would explode into smithereens. To solve that problem, the Ashwini twins substituted his head w/ that of a horse, and learnt whatever was needed from him. At the end of it all, the horse head exploded, and the twins restored Dadhichi's original head. For saving him, he gave them a promise that they could redeem anytime they liked.
Later, when Indra killed Trishiras, the son of Twastha, for conducting yagnas for the success of both devas and asuras (despite being Brihaspati's replacement as the guru of the devas), Twastha invoked Vritra from an yagna - in fact, that is how Vritrasura was created. Vritra initially played havoc w/ the devas, and Brahma revealed to Indra that only a weapon made up of the skeleton of Dadhichi - whose tapasya matched that of Twastha - could kill him. Indra then asked the Ashwinis to make that request of Dadhichi.
When requested, Dadhichi happily sat in a samadhi stance and his soul passed away, leaving his lifeless body. From his skeletal remains, Vishwakarma made the Vajra, which became the main weapon of Indra.
On the rare occasions that Dadhichi is remembered, he is remembered as one who gave up his life to save the devaas.
Anupamaa
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