The reason that Brock Lesnar will be wrestling The Undertaker at the Hell in a Cell pay-per-view event is because WWE recently changed plans for WrestleMania 32.
This match was supposed to take place at WrestleMania, but will obviously not be happening now.
WWE plans to book Seth Rollins vs. Kane in the main event for the WWE World Heavyweight Championship at the HIAC PPV.
The WWE Hell in a Cell pay-per-view event takes place October 25, 2015, at Staples Center in Los Angeles, California.. The event will air on the WWE Network and some traditional PPV outlets.
Source: WrestlingObserver.com
