Here's your 10-point cheatsheet to this big story:
Mr Yeddyurappa took oath at a low-key function at the Governor's House in Bengaluru. His cabinet will be named only after he proves his strength in a floor test at the assembly. "I seek support of all 224 legislators. I am sure they will vote according to their conscience. I am sure of winning vote of confidence and will serve 5 year term," he later said.
Governor Vala had extended invitation to the BJP after meeting both sides during the day. The formal letter was delivered to BS Yeddyurppa's house late in the evening.
The Congress, which had been prepping a petition all through Wednesday in view of such an eventuality, immediately moved to court, calling Governor's decision "an encounter of constitution".
The party also requested a freeze on the oath ceremony and contended that the long time-frame encouraged horse-trading. "It is the biggest license to poaching if the governor gives 15 days to BJP to prove majority as in earlier such cases 48 hours were given by SC," said Abhishek Singhvi, who was representing the alliance in court.
KK Venugopal, the government's former top law officer, insisted that the court could not stay the governor's decision. Senior advocate Mukul Rohatgi, representing two BJP lawmakers, said no injunction can be issued to the governor.
The top court has ordered the BJP to produce the letters submitted by BS Yeddyurappa to the governor to stake claim to form the government. "JDS and Congress outweigh the BJP. In a situation like this, on what basis has Mr Yeddyurappa claimed he has the numbers...Arithmetic defies the way he was invited," the court observed.
JD(S) leader HD Kumaraswamy alleged that the BJP promised people in his party 100 crores in cash and cabinet posts and 32 of his lawmakers have been approached by the party.
To prevent poaching, the Congress-JD(S) alliance is moving all their lawmakers out of Karnataka. Reports suggest they will be moved to Cochin.
The Congress had swiftly sealed the deal with JD(S) after being heavily outnumbered by the BJP during the counting of votes on Tuesday. The party had offered the regional JD(S) the big brother's role, offering unconditional support. On Wednesday, the alliance had staked claim at a meeting with the Governor, submitting a letter of support for JD(S) chief HD Kumaraswamy signed by 116 legislators.
The BJP contended that it should be allowed to form the government as it is the single largest party. The Congress disputed the claim, citing the precedent set by the BJP in Goa and Manipur last year. In both states, the Congress emerged the single largest party but the BJP cobbled up alliances and was invited to form the government.