For those that missed it, The Undertaker returned at the WWE Battleground pay-per-view. During the Brock Lesnar vs. Seth Rollins match, the lights went out and The Undertaker appeared in the ring. Taker then chokeslamed and hit Brock with two tombstones.
This is clearly the set up for a rematch between both men, possibly at SummerSlam. Brock Lesnar had just hit the F5 on Seth Rollins and was going for a pinfall before the lights went out and Undertaker appeared. Brock was never pinned and the match ended without a finish. Presumably, Seth Rollins won by DQ.