WWE announced the following earlier today:

Only one Superstar can run the yard in WWE, and at WrestleMania, the world will find out whether that distinction belongs to The Undertaker or Roman Reigns.

The showdown between The Phenom and The Big Dog, now confirmed for Sunday, April 2, brings into conflict the most dominant force in WrestleMania history and arguably the most powerful competitor in recent memory.

Continue reading here:  http://www.wwe.com/shows/wrestlemania/33/undertaker-vs-roman-reigns