Complex sentence: On the June 15 episode of "Raw", The Authority reinstated Brock Lesnar, who returned to the WWE and invoked his rematch clause (after losing the championship to Rollins at WrestleMania 31) to face Rollins at Battleground for the championship.
Split into simpler sentences: On the June 15 episode of "Raw", The Authority reinstated Brock Lesnar. Lesnar returned to the WWE and invoked his rematch clause (after losing the championship to Rollins at WrestleMania 31) to face Rollins at Battleground for the championship.