The Undertaker revealed in an interview with  Ariel Helwani, why he attended UFC 121 in 2010 and faced-off with Brock Lesnar.

"I was there to pick a fight. I was sent there personally to pick a fight. And I was unaware that Dana [White] had no clue what was going to happen, which I felt terrible about after. I thought there had been some discussion between him and Vince [McMahon]. I was there to pick a wrestling fight, bring him back to our world. I’m pretty gutsy, but my days of getting in an octagon had well passed me! I am smart enough to realise that."