Step 1: Irony of the fulfilment:
The story's climax turns on dramatic irony.
Final Answer:
The Maharaja vowed to personally kill 100 tigers to prove the astrologers wrong. He achieved 99 through genuine hunting, but when no tigers remained in his state, he staged the killing of an aged, sedated circus tiger to reach 100 and declare victory over fate. Ironically, it was not a real tiger but a splinter from a cheap wooden tiger toy, gifted to his son, that infected his hand and killed him — so the hundredth tiger did take his life after all.